Electrical conducting polymer, solid electrolytic capacitor and manufacturing method thereof

ABSTRACT

The present invention relates to a solid electrolytic capacitor comprising an electrode produced by forming a solid electrolytic layer comprised by a polymer having at least one repeating unit selected from a thiophene-diyl skeleton, an isothianaphthene-diyl skeleton, a pyrrole-diyl skeleton, a furan-diyl skeleton and an iminophenylene skeleton and having a fibril structure on a dielectric film layer of a porous valve-acting metal and its production method, and to a highly electroconductive polymer obtained by chemical oxidative polymerization of a monomer and an oxidizing agent at an interface and its production method.

CROSS REFERENCE

This application is an application filed under the provision of 35 USCSection 111 (a) with claiming under the provision of 35 USC Section 119(e)(i) a benefit of earlier U.S. provisional applications Serial Nos.60/129,044 and 60/129,045 both filed on Apr. 13, 1999 according to theprovision of 35 USC Section 111 (b).

TECHNICAL FIELD

The present invention relates to an electroconductive polymer, to asolid electrolytic capacitor containing an electroconductive polymer,and to methods for producing them. More specifically, the presentinvention relates to a solid electrolytic capacitor having a reducedsize, high capacity, low impedance, good moisture resistant loadingproperty and excellent heat resistance, and to a production methodthereof as well as to a highly electroconductive polymer having a novelfibril structure for use in the capacitor and to a production method ofthe highly electroconductive polymer.

BACKGROUND ART

The solid electrolytic capacitor is a capacitor element manufactured byforming a dielectric oxide film layer on an anode substrate comprising ametal foil which has a large specific surface area and has generallybeen subjected to etching treatment, forming a solid semiconductor layer(hereinafter simply referred to as a solid electrolyte) as an counterelectrode outside the dielectric layer, preferably further forming anelectrically conductive layer such as an electroconductive paste on theouter face of the electrode, and connecting a lead wire thereto. Theelement as a whole is completely sealed with an epoxy resin or the likeand is widely used as a capacitor part in electrical articles.

To cope with the demands for digitization of electrical appliances orhigher speed processing of personal computers in recent years, thecapacitor used therefor is also required to be compact, have a largecapacity and give a low impedance in a high frequency region.

As the compact capacitor having a large capacity, solid electrolyticcapacitors such as aluminum electrolytic capacitor and tantalumelectrolytic capacitor have been used. However, the aluminumelectrolytic capacitor has a problem in that since an ion conductingliquid electrolyte is used as the electrolytic solution, the impedanceis high in the high frequency region and the temperature characteristicsare bad. The tantalum electrolytic capacitor has a problem in that sincea manganese oxide is used as the electrolyte and the manganese oxide hasa relatively high resistivity, the impedance in the high frequencyregion is high.

As means to solve these problems, it has been proposed to use anelectroconductive polymer having electrically conductive properties asthe solid electrolyte. For example, use of an electroconductive organicmaterial comprising a π-conjugated polymer such as polyaniline (see,JP-A-61-239617 (the term “JP-A” as used herein means an “unexaminedpublished Japanese patent application”)), a polypyrrole (see,JP-A-61-240625), a polythiophene derivative (see, JP-A-2-15611 (U.S.Pat. No. 4,901,645)), a polyisothianaphthene not containing a dopant(see, JP-A-62-118509), a doped polyisothianaphthene (see,JP-A-62-118511) or an intrinsic conducting polymer having anelectroconductivity of from 10⁻³ to 10³ S/cm (see, JP-A-1-169914 (U.S.Pat. No. 4,803,596)) has been proposed.

That is, polymers having a conjugated double bond represented bypolymers of aniline, pyrrole, thiophene or the like generally have aspecific electroconductivity and therefore, various investigations anddevelopments have heretofore been made thereon. In particular, theelectric, magnetic and optical properties peculiar to the π-electronconjugated system of the electroconductive polymer have been takennotice of. These electroconductive polymers have been mainly produced byan electrolytic polymerization method and a chemical oxidativepolymerization method.

However, according to the conventional production method, if the lowmolecular weight polymer obtained by the redox reaction performed on theelectrode surface has poor adhesion to the electrode surface, the lowmolecular weight polymer dissolves or deposits in the electrolyticsolution. Furthermore, if an article having a large area is intended toobtain, an electrode having a size in proportion thereto must be used,accordingly, a serious problem arises with respect to the productioncost.

On the other hand, in the case of using the chemical oxidativepolymerization method, an electroconductive polymer can be easilyobtained by mixing a polymerizable monomer with an appropriate oxidizingagent, therefore, this simple polymerization method has been takennotice of in industry and studies and developments thereof have beenmade.

However, the chemical oxidative polymerization method has the followingserious problem. Since the polymerization rate is proportional to theactivity of the oxidizing agent, an oxidizing agent having high activitymust be used. But if the polymerization is performed using a highlyactive oxidizing agent, an adverse side reaction readily takes place andonly a polymer reduced in the structural order and having a lowelectroconductivity can be obtained. This problem is considered to occurbecause an electroconductive polymer having a conjugated double bondproduced stays in the reaction system for a long period of time,therefore, the polymer skeleton having the conjugated double bond ispartially destroyed by the effect of excess oxidizing agent in thereaction system, as a result, the electroconductivity decreases.

Furthermore, the electroconductive polymer obtained by the electrolyticpolymerization or chemical oxidative polymerization is generallyinsoluble and infusible, therefore, there is an operational problemparticularly in that its after processing is very difficult.

In order to solve these problems, various attempts have been made. Forexample, JP-A-7-130579 (U.S. Pat. No. 5,567,209) discloses a productionmethod of a solid electrolytic capacitor using an oxide film formed on avalve-acting metal as the dielectric layer and an electroconductivepolymer formed on the dielectric layer as the solid electrolytecomprising a step of coating a monomer compound solution on the surfaceof the above-described dielectric oxide layer and drying it to form asolid monomer compound, and a step of contacting the solid monomercompound with an oxidizing agent solution to form an electroconductivepolymer layer, thereby producing a solid electrolytic capacitor having ahigh capacity occurrence ratio and good high-frequency properties.

JP-A-6-340754 discloses a technique of allowing polycyclic aromaticamine compound to adhere to or impregnate into an insulating substrateand contacting the substrate with a solution containing an oxidizingagent to thereby oxidatively polymerize the polycyclic aromatic aminecompound inside or on the surface of the substrate.

JP-A-10-50558 discloses a production method of a solid electrolyticcapacitor as an application of the electroconductive polymer, comprisingimpregnating an electroconductive polymer as the cathode electrolyteinto a capacitor element comprising an anode member having thereon achemical formed layer, wherein the capacitor element is immersed in asolution obtained by dissolving an oxidizing agent in a monomer whichbecomes an electroconductive polymer by the oxidative polymerization,thereby forming an electroconductive polymer layer within the capacitorelement, so that a compact capacitor having a large capacity can beproduced.

JP-A-10-50559 discloses a technique, which is an application of theelectroconductive polymer to a solid electrolytic capacitor comprising astep of immersing a capacitor element in an oxidizing agent solution andthen evaporating the solvent component, thereby precipitating anoxidizing agent within the capacitor element, and a step of immersingthe capacitor element in a solution containing a monomer which becomesan electroconductive polymer by the oxidative polymerization, therebyallowing the oxidizing agent to act on the monomer, so thathigh-temperature load properties can be improved.

Furthermore, JP-A-9-289141 (EP-A-803885) proposes a production method ofa solid electrolytic capacitor, comprising immersing a porous electrodematerial in a monomer salt solution kept at a temperature higher thanthe dissolution temperature, cooling the porous material to precipitatethe monomer salt on the surface thereof, and immersing the porousmaterial in a solution containing an oxidizing agent.

As a solid electrolyte formed on the dielectric film layer, anelectroconductive metal oxide and an electroconductive polymer have beenhad attention because they are expected to be basically possible forattaining a sufficiently high electroconductivity. However, they have aproblem in that if the electroconductivity exceeds the proper range, theleakage current greatly increases to cause short circuit, whereas if theelectroconductivity is low, the frequency properties are deterioratedand the capacity greatly decreases. As such, the control of theelectroconductivity to fall within a proper range and the thermalstability of the solid electrolyte are still in need of improvement.

Conventional capacitors using an electroconductive polymer such aspolypyrrole have a problem that the capacitor properties greatlyfluctuate depending on the moisture resistance under load. In connectiontherewith, heat resistance is keenly demanded. For example, theresistance to heat by reflow soldering property at the formation from acapacitor element into a capacitor part is important and a capacitorelement having high heat resistance is demanded. In other words,conventional techniques have a problem in the solid electrolyte producedon the oxide film layer and the production method thereof.

Specifically, the technique disclosed in JP-A-7-130579 (U.S. Pat. No.5,567,209), in which the monomer compound solution is dried to form asolid-like monomer, has a problem in that the polymerization rate maydecrease as the polymerization degree of the polymer compositionincreases since the diffusion of monomers are restricted in the solidmonomer phase.

The technique disclosed in JP-A-6-340754 relates to a method for forminga transparent electroconductive thin film on an insulting material, anddoes not refer to the shape or performance of the polymer which has afibril structure obtained by the polymerization positively effected atthe interface.

The technique disclosed in JP-A-10-50558 is a technique of forming anelectroconductive polymer thin film on a chemical formed film layer butan oxidizing agent is dissolved directly in the monomer which becomes anelectroconductive polymer by the oxidative polymerization, therefore,the oxidative polymerization also proceeds in the monomer solution toform a polymer before and while it is used and it is difficult tomaintain a uniform monomer solution all the time. Thus, this is anunstable production method failing in bringing out stable performance.

According to the technique disclosed in JP-A-10-50559, an oxidizingagent solution is introduced into pores, the solvent is evaporated toprecipitate crystals of the oxidizing agent, and then the oxidativepolymerization is performed. In view of the process, however, this is aninefficient production method in industry because a step ofprecipitating the oxidizing agent into pores on the chemical formedsurface of a metal foil is indispensable and as duly understood, thearea where the solid oxidizing agent contacts with the monomer is verysmall, therefore, the polymerization reaction proceeds slowly.

Furthermore, the technique disclosed in JP-A-9-289141 (EP-A-803885), inwhich the polymerizable monomer is solid has the same problem as in thetechnique disclosed in JP-A-10-50559.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a highlyelectroconductive polymer having a conjugated double bond (π electronconjugated system) used advantageously as a solid electrolyte for asolid electrolytic capacitor.

Another object of the present invention is to provide a method forproducing the above novel polymer having a conjugated double bond by wayof oxidative polymerization, which polymer has an higherelectroconductivity than other polymers having the same chemicalcomposition.

Still another object of the present invention is to provide a solidelectrolytic capacitor comprising the above highly electroconductivepolymer as a solid electrolyte and having not only good initialproperties but also excellent long-term reliability such as durabilityat high temperature and high humidity and a method for producing thesame.

As a result of extensive investigations under these circumstances, ithas been first found that slowly contacting a solution having dissolvedtherein a polymerizable monomer alone or together with an electrolytehaving a doping action with a solution of an oxidizing agent having apolymerization initiating ability on an interface to polymerize themonomer can give rise to a highly electroconductive polymer having ascaly fibrillar structure and that practicing this polymerization methodon a dielectric film layer and utilizing the resulting film compositionhaving a fibril structure as a solid electrolyte can provide a capacitorexcellent in initial properties (loss factor, leakage current, heatresistance, equivalent series resistance in high frequency regions, lowimpedance, etc.) and long term reliability (durability at hightemperature and high humidity, etc.). The present invention has beenaccomplished based on this finding.

Therefore, the present invention provides the following solidelectrolytic capacitor, its production method, electroconductive polymerand its production method:

[1] A solid electrolytic capacitor comprising a dielectric film layer ona porous valve-acting metal and a solid electrolytic layer comprised bya polymer having a fibril structure formed on said dielectric filmlayer.

[2] The solid electrolytic capacitor as described in [1] above, whereinthe solid polymer electrolytic layer is an electroconductive polymerhaving a fibril structure comprising as a repeating unit a structurehaving a thiophene-diyl skeleton represented by the following generalformula (1):

(wherein R¹ and R² each independently represent a monovalent groupselected from the group consisting of a hydrogen atom, a linear orbranched, saturated or unsaturated alkyl, alkoxy or alkyl ester grouphaving from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyanogroup, a primary, secondary or tertiary amino group, a CF₃ group, aphenyl group and a substituted phenyl group, the hydrocarbon chains ofR¹ and R² may combine with each other at any position to form a divalentchain for forming a 3-, 4-, 5-, 6- or 7-membered saturated orunsaturated hydrocarbon cyclic structure together with the carbon atomssubstituted by R¹ and R², the cyclic bonded chain may optionally containa bond such as carbonyl, ether, ester, amide, sulfide, sulfinyl,sulfonyl and imino at any position, δ represents a number in the rangeof from 0 to 1, Z represents an anion, and j represents a valence of Zand is 1 or 2).

[3] The solid electrolytic capacitor as described in [1] above, whereinthe solid polymer electrolytic layer is an electroconductive polymerhaving a fibril structure comprising as a repeating unit a structurehaving a condensed polycyclic skeleton represented by the followinggeneral formula (2):

(wherein R³, R⁴, R⁵, R⁶, R⁷ and R⁸ each independently represent amonovalent group selected from the group consisting of a hydrogen atom,a linear or branched, saturated or unsaturated alkyl, alkoxy or alkylester group having from 1 to 10 carbon atoms, a halogen atom, a nitrogroup, a cyano group, a primary, secondary or tertiary amino group, aCF₃ group, a phenyl group and a substituted phenyl group, thehydrocarbon chains of R³, R⁴, R⁵, R⁶, R⁷ or R⁸ may combine with eachother at any position to form a divalent chain for forming at least one3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclicstructure together with the carbon atoms substituted by R³, R⁴, R⁵, R⁶,R⁷ or R⁸, the cyclic bonded chain may optionally contain a bond such ascarbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino atany position, k represents the number of condensed rings surrounded bythe thiophene ring and the benzene ring having the substituents R³ to R⁶and is 0 or an integer of from 1 to 3, the condensed ring in the formulamay contain an optional number of nitrogen or N-oxide, with the provisothat the substituents R³ to R⁸ are deducted by the number of nitrogen orN-oxide, δ represents a number in the range of from 0 to 1, Z representsan anion, and j represents a valence of Z and is 1 or 2).

[4] The solid electrolytic capacitor as described in [1] above, whereinsaid solid polymer electrolytic layer is an electroconductive polymerhaving a fibril structure comprising as a repeating unit a structurehaving a pyrrole-diyl skeleton represented by the following generalformula (3):

(wherein R⁹ and R¹⁰ each independently represent a monovalent groupselected from the group consisting of a hydrogen atom, a linear orbranched, saturated or unsaturated alkyl, alkoxy or alkyl ester grouphaving from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyanogroup, a primary, secondary or tertiary amino group, a CF₃ group, aphenyl group and a substituted phenyl group, the hydrocarbon chains ofR⁹ and R¹⁰ may combine with each other at an optional position to form adivalent chain for forming at least one 3-, 4-, 5-, 6- or 7-memberedsaturated or unsaturated hydrocarbon cyclic structure together with thecarbon atoms substituted by R⁹ and R¹⁰, and the cyclic bonded chain mayoptionally contain a bond such as carbonyl, ether, ester, amide,sulfide, sulfinyl, sulfonyl and imino at any position, δ represents anumber in the range of from 0 to 1, Z represents an anion, and jrepresents a valence of Z and is 1 or 2).

[5] The solid electrolytic capacitor as described in [1] above, whereinthe solid polymer electrolytic layer is an electroconductive polymerhaving a fibril structure comprising as a repeating unit a structurehaving a furan-diyl skeleton represented by the following generalformula (4):

(wherein the substituents R¹¹ and R¹² each independently represent amonovalent group selected from the group consisting of a hydrogen atom,a linear or branched, saturated or unsaturated alkyl, alkoxy or alkylester group having from 1 to 10 carbon atoms, a halogen atom, a nitrogroup, a cyano group, a primary, secondary or tertiary amino group, aCF₃ group, a phenyl group and a substituted phenyl group, thehydrocarbon chains of R¹¹ and R¹² may combine with each other at anyposition to form a divalent chain for forming at least one 3-, 4-, 5-,6- or 7-membered saturated or unsaturated hydrocarbon cyclic structuretogether with the carbon atoms substituted by R¹¹ and R¹², the cyclicbonded chain may optionally contain a bond such as carbonyl, ether,ester, amide, sulfide, sulfinyl, sulfonyl and imino at any position, δrepresents a number in the range of from 0 to 1, Z represents an anion,and j represents a valence of Z and is 1 or 2).

[6] The solid electrolytic capacitor as described in [1] above, whereinthe solid polymer electrolytic layer is an electroconductive polymerhaving a fibril structure comprising as a repeating unit a structurehaving an iminophenylene skeleton represented by the following generalformula (5):

(wherein the substituents R¹³, R¹⁴, R¹⁵ and R¹⁶ each independentlyrepresent a monovalent group selected from the group consisting of ahydrogen atom, a linear or branched, saturated or unsaturated alkyl,alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogenatom, a nitro group, a cyano group, a primary, secondary or tertiaryamino group, a CF₃ group, a phenyl group and a substituted phenyl group,the hydrocarbon chains of R¹³, R¹⁴, R¹⁵ or R¹⁶ may combine with eachother at any position to form a divalent chain for forming at least one3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclicstructure together with the carbon atoms substituted by R¹³, R¹⁴, R¹⁵ orR¹⁶, the cyclic bonded chain may optionally contain a bond such ascarbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino atany position, δ represents a number in the range of from 0 to 1, Zrepresents an anion, and j represents a valence of Z and is 1 or 2).

[7] The solid electrolytic capacitor as described in [1] above, whereinsaid solid polymer electrolyte has an electroconductivity of from about0.1 to about 200 S/cm.

[8] A method for producing a solid electrolytic capacitor comprising asolid electrolytic layer composed of a polymer having a fibril structureon a dielectric film layer of a porous valve-acting metal, whichcomprises the step of contacting a polymerizable monomer with a singlesolution containing an oxidizing agent having a polymerizationinitiating ability kept in the saturated or supersaturated state or amixed solution containing the oxidizing agent and an electrolyte havinga doping action on said dielectric film, thereby forming a compositionin the form of a film of a polymer having a fibril structure on saiddielectric film.

[9] A method for producing a solid electrolytic capacitor, comprising asolid electrolytic layer composed of a polymer having a fibril structureon a dielectric film layer of a porous valve-acting metal, whichcomprises the step of contacting a solution having dissolved therein apolymerizable monomer alone or together with an electrolyte having adoping action with a single solution containing an oxidizing agenthaving a polymerization initiating ability kept in the saturated orsupersaturated state or a mixed solution containing the oxidizing agentand an electrolyte having a doping action on said dielectric film,thereby forming a composition in the form of a film of a polymer havinga fibril structure on said dielectric film.

[10] The method for producing a solid electrolytic capacitor asdescribed in [8] above, which comprises the step of contacting on saiddielectric film a polymerizable monomer represented by the followinggeneral formula (6):

(wherein R¹ and R² each independently represent a monovalent groupselected from the group consisting of a hydrogen atom, a linear orbranched, saturated or unsaturated alkyl, alkoxy or alkyl ester grouphaving from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyanogroup, a primary, secondary or tertiary amino group, a trihalomethylgroup, a phenyl group and a substituted phenyl group, the hydrocarbonchains of R¹ and R² may combine with each other at any position to forma divalent chain for forming a 3-, 4-, 5-, 6- or 7-membered saturated orunsaturated hydrocarbon cyclic structure together with the carbon atomssubstituted by R¹ and R², the cyclic bonded chain may optionally containa bond such as carbonyl, ether, ester, amide, sulfide, sulfinyl,sulfonyl and imino at any position) with a solution containing anoxidizing agent having a polymerization initiating ability, therebyforming a composition in the form of a film of a polymer having a fibrilstructure on said dielectric film.

[11] The method for producing a solid electrolytic capacitor asdescribed in [8] above, which comprises the step of contacting on saiddielectric film a polymerizable monomer represented by the followinggeneral formula (7):

(wherein the substituents R³, R⁴, R⁵, R⁶, R⁷ and R⁸ each independentlyrepresent a monovalent group selected from the group consisting of ahydrogen atom, a linear or branched, saturated or unsaturated alkyl,alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogenatom, a nitro group, a cyano group, a primary, secondary or tertiaryamino group, a CF₃ group, a phenyl group and a substituted phenyl group,the hydrocarbon chains of R³, R⁴, R⁵, R⁶, R⁷ or R⁸ may combine with eachother at any position to form a divalent chain for forming at least one3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclicstructure together with the carbon atoms substituted by R³, R⁴, R⁵, R⁶,R⁷ or R⁸, the cyclic bonded chain may optionally contain a bond such ascarbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino atany position, k represents the number of condensed rings surrounded bythe thiophene ring and the benzene ring having the substituents R³ to R⁶and is 0 or an integer of from 1 to 3, the condensed ring in the formulamay contain an optional number of nitrogen or N-oxide, with the provisothat the substituents R³ to R⁸ are deducted by the number of nitrogen orN-oxide) with a solution containing an oxidizing agent having apolymerization initiating ability, thereby forming a composition in theform of a film of a polymer having a fibril structure on said dielectricfilm.

[12] The method for producing a solid electrolytic capacitor asdescribed in [8] above, which comprises the step of contacting on saiddielectric film a polymerizable monomer represented by the followinggeneral formula (8):

(wherein the substituents R⁹ and R¹⁰ each independently represent amonovalent group selected from the group consisting of a hydrogen atom,a linear or branched, saturated or unsaturated alkyl, alkoxy or alkylester group having from 1 to 10 carbon atoms, a halogen atom, a nitrogroup, a cyano group, a primary, secondary or tertiary amino group, aCF₃ group, a phenyl group and a substituted phenyl group, thehydrocarbon chains of R⁹ and R¹⁰ may combine with each other at anoptional position to form a divalent chain for forming at least one 3-,4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclicstructure together with the carbon atoms substituted by R⁹ and R¹⁰, andthe cyclic bonded chain may optionally contain a bond such as carbonyl,ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino at anyposition) with a solution containing an oxidizing agent having apolymerization initiating ability, thereby forming a composition in theform of a film of a polymer having a fibril structure on said dielectricfilm.

[13] The method for producing a solid electrolytic capacitor asdescribed in [8] above, which comprises the step of contacting on saiddielectric film a polymerizable monomer represented by the followinggeneral formula (9):

(wherein the substituents R¹¹ and R¹² each independently represent amonovalent group selected from the group consisting of a hydrogen atom,a linear or branched, saturated or unsaturated alkyl, alkoxy or alkylester group having from 1 to 10 carbon atoms, a halogen atom, a nitrogroup, a cyano group, a primary, secondary or tertiary amino group, aCF₃ group, a phenyl group and a substituted phenyl group, thehydrocarbon chains of R¹¹ and R¹² may combine with each other at anyposition to form a divalent chain for forming at least one 3-, 4-, 5-,6- or 7-membered saturated or unsaturated hydrocarbon cyclic structuretogether with the carbon atoms substituted by R¹¹ and R¹², the cyclicbonded chain may optionally contain a bond such as carbonyl, ether,ester, amide, sulfide, sulfinyl, sulfonyl and imino at any position)with a solution containing an oxidizing agent having a polymerizationinitiating ability, thereby forming a composition in the form of a filmof a polymer having a fibril structure on said dielectric film.

[14] The method for producing a solid electrolytic capacitor asdescribed in [8] above, which comprises the step of contacting on saiddielectric film a polymerizable monomer represented by the followinggeneral formula (10):

(wherein the substituents R¹³, R¹⁴, R¹⁵ and R¹⁶ each independentlyrepresent a monovalent group selected from the group consisting of ahydrogen atom, a linear or branched, saturated or unsaturated alkyl,alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogenatom, a nitro group, a cyano group, a primary, secondary or tertiaryamino group, a CF₃ group, a phenyl group and a substituted phenyl group,the hydrocarbon chains of R¹³, R¹⁴, R¹⁵ or R¹⁶ may combine with eachother at any position to form a divalent chain for forming at least one3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclicstructure together with the carbon atoms substituted by R¹³, R¹⁴, R¹⁵ orR¹⁶, the cyclic bonded chain may optionally contain a bond such ascarbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino atany position) with a solution containing an oxidizing agent having apolymerization initiating ability, thereby forming a composition in theform of a film of a polymer having a fibril structure on said dielectricfilm.

[15] The method for producing a solid electrolytic capacitor asdescribed in [9] above, wherein the polymerizable monomer has aconcentration of from 0.01 to 5 mol/L.

[16] The method for producing a solid electrolytic capacitor asdescribed in [8] above, wherein the electrolyte having a doping actionhas a concentration of from 0.001 to 2.5 mol/L.

[17] The method for producing a solid electrolytic capacitor asdescribed in [8] above, wherein the oxidizing agent having apolymerization initiating ability is at least one compound selected frompersulfates, bichromates and trivalent iron salts.

[18] The method for producing a solid electrolytic capacitor asdescribed in [8] above, wherein the concentration of the oxidizing agenthaving a polymerization initiating ability is from 0.01 to 5 times theconcentration of the polymerizable monomer.

[19] The method for producing a solid electrolytic capacitor asdescribed in [8] above, wherein the step of forming a solid polymerelectrolyte is repeated from 2 to 30 times to form compositions each ofwhich is in the form of a film.

[20] A highly electroconductive polymer having a fibril structurecomprising as a repeating unit a structure having a thiophene-diylskeleton represented by the following general formula (1):

(wherein the substituents R¹ and R² each independently represent amonovalent group selected from the group consisting of a hydrogen atom,a linear or branched, saturated or unsaturated alkyl, alkoxy or alkylester group having from 1 to 10 carbon atoms, a halogen atom, a nitrogroup, a cyano group, a primary, secondary or tertiary amino group, aCF₃ group, a phenyl group and a substituted phenyl group. Thehydrocarbon chains of R¹ and R² may combine with each other at anyposition to form a divalent chain for forming a 3-, 4-, 5-, 6- or7-membered saturated or unsaturated hydrocarbon cyclic structuretogether with the carbon atoms substituted by R¹ and R², the cyclicbonded chain may optionally contain a bond such as carbonyl, ether,ester, amide, sulfide, sulfinyl, sulfonyl and imino at any position, δrepresents a number in the range of from 0 to 1, Z represents an anion,and j represents a valence of Z and is 1 or 2).

[21] A highly electroconductive polymer having a fibril structurecomprising as a repeating unit a structure having a condensed heterapolycyclic skeleton represented by the following general formula (2):

(wherein the substituents of R³, R⁴, R⁵, R⁶, R⁷ and R⁸ eachindependently represent a monovalent group selected from the groupconsisting of a hydrogen atom, a linear or branched, saturated orunsaturated alkyl, alkoxy and alkyl ester group having from 1 to 10carbon atoms, a halogen atom, a nitro group, a cyano group, a primary,secondary or tertiary amino group, a CF₃ group, a phenyl group and asubstituted phenyl group. The hydrocarbon chains of R³, R⁴, R⁵, R⁶, R⁷or R⁸ may combine with each other at any position to form a divalentchain for forming at least one 3-, 4-, 5-, 6- or 7-membered saturated orunsaturated hydrocarbon cyclic structure together with the carbon atomssubstituted by R³, R⁴, R⁵, R⁶, R⁷ or R⁸, the cyclic bonded chain mayoptionally contain a bond such as carbonyl, ether, ester, amide,sulfide, sulfinyl, sulfonyl and imino at any position, k represents thenumber of condensed rings surrounded by the thiophene ring and thebenzene ring having the substituents R³ to R⁶ and is 0 or an integer offrom 1 to 3, the condensed ring in the formula may optionally containnitrogen or N-oxide, with the proviso that the substituents R³ to R⁸ arededucted by the number of nitrogen or N-oxide, δ represents a number inthe range of from 0 to 1, Z represents an anion, and j represents avalence of Z and is 1 or 2).

[22] A highly electroconductive polymer having a fibril structurecomprising as a repeating unit a structure having a pyrrole-diylskeleton represented by the following general formula (3):

(wherein R⁹ and R¹⁰ each independently represent a monovalent groupselected from the group consisting of a hydrogen atom, a linear orbranched, saturated or unsaturated alkyl, alkoxy or alkyl ester grouphaving from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyanogroup, a primary, secondary or tertiary amino group, a CF₃ group, aphenyl group and a substituted phenyl group, the hydrocarbon chains ofR⁹ and R¹⁰ may combine with each other at an optional position to form adivalent chain for forming at least one 3-, 4-, 5-, 6- or 7-memberedsaturated or unsaturated hydrocarbon cyclic structure together with thecarbon atoms substituted by R⁹ and R¹⁰, and the cyclic bonded chain mayoptionally contain a bond such as carbonyl, ether, ester, amide,sulfide, sulfinyl, sulfonyl and imino at any position, δ represents anumber in the range of from 0 to 1, Z represents an anion, and jrepresents a valence of Z and is 1 or 2).

[23] A highly electroconductive polymer having a fibril structurecomprising as a repeating unit a structure having a furan-diyl skeletonrepresented by the following general formula (4):

(wherein the substituents R¹¹ and R¹² each independently represent amonovalent group selected from the group consisting of a hydrogen atom,a linear or branched, saturated or unsaturated alkyl, alkoxy or alkylester group having from 1 to 10 carbon atoms, a halogen atom, a nitrogroup, a cyano group, a primary, secondary or tertiary amino group, aCF₃ group, a phenyl group and a substituted phenyl group, thehydrocarbon chains of R¹¹ and R¹² may combine with each other at anyposition to form a divalent chain for forming at least one 3-, 4-, 5-,6- or 7-membered saturated or unsaturated hydrocarbon cyclic structuretogether with the carbon atoms substituted by R¹¹ and R¹², the cyclicbonded chain may optionally contain a bond such as carbonyl, ether,ester, amide, sulfide, sulfinyl, sulfonyl and imino at any position, δrepresents a number in the range of from 0 to 1, Z represents an anion,and j represents a valence of Z and is 1 or 2).

[24] A highly electroconductive polymer having a fibril structurecomprising as a repeating unit a structure having an iminophenyleneskeleton represented by the following general formula (5):

(wherein the substituents R¹³, R¹⁴, R¹⁵ and R¹⁶ each independentlyrepresent a monovalent group selected from the group consisting of ahydrogen atom, a linear or branched, saturated or unsaturated alkyl,alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogenatom, a nitro group, a cyano group, a primary, secondary or tertiaryamino group, a CF₃ group, a phenyl group and a substituted phenyl group,the hydrocarbon chains of R¹³, R¹⁴, R¹⁵ or R¹⁶ may combine with eachother at any position to form a divalent chain for forming at least one3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclicstructure together with the carbon atoms substituted by R¹³, R¹⁴, R¹⁵ orR¹⁶, the cyclic bonded chain may optionally contain a bond such ascarbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino atany position, δ represents a number in the range of from 0 to 1, Zrepresents an anion, and j represents a valence of Z and is 1 or 2).

[25] A method for producing a highly electroconductive polymer having afibril structure, comprising contacting at least one polymerizablemonomer represented by the following general formula (6):

(wherein R¹ and R² have the same meanings as in [10] above); the generalformula (7):

(wherein R³, R⁴, R⁵, R⁶, R⁷ and R⁸ have the same meanings as in [11]above); the general formula (8):

(wherein R⁹ and R¹⁰ have the same meanings as in [12] above); thegeneral formula (9):

(wherein R¹¹ and R¹² have the same meanings as in [13] above); or thegeneral formula (10):

(wherein R¹³, R¹⁴, R¹⁵ and R¹⁶ have the same meanings as in [14] above)with a solution containing an oxidizing agent having a polymerizationinitiating ability such that an interface is formed therebetween, andperforming polymerization at said interface.

[26] The method for producing a highly electroconductive polymer havinga fibril structure as described in [25] above, comprising contacting asolution obtained by dissolving at least one polymerizable monomerrepresented by formula (6), (7), (8), (9) or (10) as described in [25]above in a solvent with a solution containing an oxidizing agent havinga polymerization initiating ability such that an interface is formedtherebetween, and performing polymerization at said interface.

[27] The method for producing a highly electroconductive polymer havinga fibril structure as described in [25] above, wherein the solutioncontaining an oxidizing agent having a polymerization initiating abilitycontains an electrolyte having a doping action.

[28] The method for producing a highly electroconductive polymer havinga fibril structure as described in [25] above, wherein the solutioncontaining an oxidizing agent having a polymerization initiating abilityis a saturated or supersaturated solution.

[29] The method for producing a highly electroconductive polymer havinga fibril structure as described in [25] above, wherein a saturatedsolution of an oxidizing agent having a polymerization initiatingability is produced, the oxidizing agent solution is contacted with thepolymerizable monomer at a temperature lower than the temperature at theproduction of said saturated solution to form a interface, and thenpolymerization is performed.

[30] The method for producing a highly electroconductive polymer havinga fibril structure as described in [25] above, wherein the oxidizingagent having a polymerization initiating agent is at least one of apersulfate, a bichromate and a trivalent iron salt.

[31] The method for producing a highly electroconductive polymer havinga fibril structure as described in [26] above, wherein the solvent is ahydrophilic organic solvent capable of dissolving the polymerizablemonomer.

[32] The method for producing a highly electroconductive polymer havinga fibril structure as described in [25] above, wherein the polymerizablemonomer is contacted with the solution containing an oxidizing agent toproduce a highly electroconductive polymer having a fibril structure andafter washing or not washing the polymer, the method for producing ahighly electroconductive polymer having a fibril structure described in[25] above is performed two or more times on the surface of the highlyelectroconductive polymer having a fibril structure to stack polymercomposition layers.

[33] The method for producing a highly electroconductive polymer havinga fibril structure as described in [26] above, wherein the polymerizablemonomer is contacted with the solution containing an oxidizing agent toproduce a highly electroconductive polymer having a fibril structure andafter washing or not washing the polymer, the method for producing ahighly electroconductive polymer having a fibril structure described in[26] above is performed two or more times on the surface of the highlyelectroconductive polymer having a fibril structure to stack polymercomposition layers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photograph (×50,000) by scanning electron microscopy of thecross section of an anode aluminum foil having formed thereon anelectroconductive polymer layer obtained in Example 1 of the presentinvention.

FIG. 2 is a photograph (×50,000) by scanning electron microscopy of aformed aluminum foil.

FIG. 3 is a photograph (×5,100) by scanning electron microscopy of thehighly electroconductive polymer of 3,4-ethylenedioxythiophene, whereinthe polymer was obtained in Example 14.

FIG. 4 is an enlarged photograph (×50,000) by scanning electronmicroscopy of the fibril structure moiety of the highlyelectroconductive polymer of FIG. 3.

FIG. 5 is a photograph (×50,000) by scanning electron microscopy of the3,4-ethylenedioxythiophene polymer obtained in Comparative Example 3.

FIG. 6 is a photograph (×2,000) by scanning electron microscopy of thehighly electroconductive polymer of 3,4-ethylenedioxythiophene, whereinthe polymer was obtained in Example 15.

FIG. 7 is an enlarged photograph (×20,000) by scanning electronmicroscopy of the fibril structure moiety of the highlyelectroconductive polymer of FIG. 6.

FIG. 8 is a photograph (×50,000) by scanning electron microscopy of thefibril structure moiety for highly electroconductive polymer of1,3-dihydroisothianaphthene, wherein the polymer was obtained in Example16.

FIG. 9 is a photograph (×50,000) by scanning electron microscopy of the1,3-dihydroisothianaphthene polymer obtained in Comparative Example 4.

DETAILED DESCRIPTION OF THE INVENTION

The highly electroconductive polymer having a fibril structurecomprising a chemical structure represented by formula (1), (2), (3),(4) or (5) as a repeating unit according to the present invention hasheretofore not been present. This is apparent from the fact that thedifference between this polymer and the polymer produced using apolymerizable monomer (6), (7), (8), (9) or (10) and an oxidizing agenthaving a polymerization initiating ability under the stirring conditioncan be clearly seen from the comparison between FIG. 4, 7 or 8 showing afibril structure and FIG. 5 or 9 not showing a fibril structure. Inparticular, as is apparent from the Examples 13, 14, 16, and 17 andComparative Examples 2, 3, 4 and 5 which will be described later, thosehaving a fibril structure and those not having a fibril structuregreatly differ in the electroconductivity.

Although the specific reason why the polymer having a fibril structureaccording to the present invention shows high electroconductivity isunclear, one of causes therefor is considered that in the presentinvention, a solution containing an oxidizing agent having apolymerization initiating ability, preferably a solution having a highconcentration, more preferably a saturated or supersaturated solution(hereinafter these two solutions are simply referred to as “a saturatedsolution and the like”) is calmly contacted with a polymerizable monomeror a solution containing a polymerizable monomer so as to form aninterface (the “interface” as used in the present invention means one insuch a state such that mutual dissolution partially takes place at thesurface where an oxidizing agent solution layer contacts a polymerizablemonomer layer or a solution layer containing a polymerizable monomer anddespite the presence of a layer graded in the concentration, respectivelayers are individually present) and the polymerization proceeds at thisinterface, therefore, the electroconductive polymer produced is free ofeffect of excess oxidizing agent and the structural regularity thereofis not destroyed.

As another reason, it is considered that an oxidizing agent is used inthe form of a high concentration solution or a saturated solution andthe like and at this time, the oxidizing agent seems to be present inthe state of a very small crystal nucleus, therefore, polymerization ofthe polymerizable monomer proceeds on the limited reaction field on thecrystal nucleus surface, as a result, the highly electroconductivepolymer produced has a high steric order. By these two reasons, a highlyelectroconductive polymer having an electroconductivity as high as from10 to 1,000 times the electroconductivity of a polymer having the samecomposition obtained from the same polymerizable monomer is consideredto yield and appear as a fibril structure in the image by scanningelectron microscopy (SEM).

Examples of the thiophene derivative represented by general formula (6)as a starting material of the highly electroconductive polymer include3-methylthiophene, 3-ethylthiophene, 3-propylthiophene,3-butylthiophene, 3-pentylthiophene, 3-hexylthiophene,3-heptylthiophene, 3-octylthiophene, 3-nonylthiophene, 3-decylthiophene,3-fluorothiophene, 3-chlorothiophene, 3-bromothiophene,3-cyanothiophene, 3,4-methylenedioxythiophene, 3,4-ethylenedioxythiophene and 3,4-propylenedioxythiophene. However, the presentinvention is by no means limited thereto.

Specific examples of the condensed heteropolycyclic compound representedby general formula (7) as a starting material of the highlyelectroconductive polymer include compounds having a1,3-dihydroisothianaphthene skeleton (another name:1,3-dihydrobenzo[c]thiophene) when k is 0, compounds having a1,3-dihydronaphtho[2,3-c]thiophene skeleton when k is 1, compoundshaving a 1,3-dihydroanthra[2,3-c]thiophene skeleton and compounds havinga 1,3-dihydronaphthaceno[2,3-c]thiophene skeleton. However, the presentinvention is by no means limited thereto.

The condensed heteropolycyclic compound of general formula (7) where twoadjacent substituents out of the substituents R³, R⁴, R⁵ and R⁶ arecombined with each other through an unsaturated bond to form a condensed6-membered ring (ortho substitution) may also be used and examplesthereof include 1,3-dihydronaphtho[1,2-c] thiophene derivatives when kis 0, 1,3-dihydrophenanthra[2,3-c]thiophene derivatives and1,3-dihydrotriphenylo[2,3-c]thiophene derivatives when k is 1 and1,3-dihydrobenzo[a]anthraceno[7,8-c]thiophene derivatives when k is 2.However, the present invention is by no means limited thereto.

Furthermore, the condensed ring may optionally contain nitrogen orN-oxide and examples thereof include1,3-dihydrothieno[3,4-b]quinoxaline,1,3-dihydrothieno[3,4-b]quinoxaline-4-oxide and1,3-dihydrothieno[3,4-b]quinoxaline-4,9-dioxide when k is 0. However,the present invention is by no means limited thereto.

Examples of the pyrrole derivative represented by general formula (8) asa starting material of the highly electroconductive polymer includederivatives such as 3-methylpyrrole, 3-ethylpyrrole, 3-propylpyrrole,3-butylpyrrole, 3-pentylpyrrole, 3-hexylpyrrole, 3-heptylpyrrole,3-octylpyrrole, 3-nonylpyrrole, 3-decylpyrrole, 3-fluoropyrrole,3-chloropyrrole, 3-bromopyrrole, 3-cyanopyrrole,3,4-methylenedioxypyrrole, 3,4-ethylenedioxypyrrole,3,4-propylenedioxypyrrole, 3,4-dimethylpyrrole, 3,4-diethylpyrrole.However, the present invention is by no means limited thereto.

Examples of the furan derivative represented by general formula (9) as astarting material of the highly electroconductive polymer includederivatives such as 3-methylfuran, 3-ethylfuran, 3-propylfuran,3-butylfuran, 3-pentylfuran, 3-hexylfuran, 3-heptylfuran, 3-octylfuran,3-nonylfuran, 3-decylfuran, 3-fluorofuran, 3-chlorofuran, 3-bromofuran,3-cyanofuran, 3,4-methylenedioxyfuran, 3,4-ethylenedioxyfuran,3,4-propylenedioxyfuran. However, the present invention is by no meanslimited thereto.

Examples of the aniline derivative represented by general formula (10)as a starting material of the highly electroconductive polymer includederivatives such as 2-methylaniline, 2-ethylaniline, 2-propylaniline,2-butylaniline, 2-pentylaniline, 2-hexylaniline, 2-heptylaniline,2-octylaniline, 2-nonylaniline, 2-decylaniline, 2-fluoroaniline,2-chloroaniline, 2-bromoaniline and 2-cyanoaniline. However, the presentinvention is by no means limited thereto.

Preferred examples of the substituted phenyl group described in theabove general formulae (1) to (10) include phenyl groups substituted atany of o-, m-, or p-position with at least one member selected from thegroup consisting of a CF₃ group, Br, Cl, F, a methyl group, an ethylgroup, a cyano group, and a nitro group.

Examples of the valve-acting metal which can be used in the solidelectrolytic capacitor of the present invention include a single metalsuch as aluminum, tantalum, niobium, titanium, zirconium, magnesium orsilicon, and an alloy thereof. The metal may have any shape as far as ithas a porous formed shape, and examples thereof include a rolled foilsubjected to etching and a powder sintered body.

The oxidizing agent for use in the production of an electroconductivepolymer of the present invention may be any as far as the oxidizingagent can satisfactorily attain dehydrogenating four electron oxidationreaction, and a compound which is industrially inexpensive and easy tohandle in the production is preferred. Specific examples thereof includeFe(III)-type compounds such as FeCl₃, Fe(ClO₄)₃ and Fe (organic acidanion) salt, anhydrous aluminum chloride/cuprous chloride, alkali metalpersulfates, ammonium persulfates, peroxides, manganates such aspotassium permanganate, quinones such as2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ),tetrachloro-1,4-benzoquinone and tetracyano-1,4-benzoquinone, halogenssuch as iodine and bromine, peracid, sulfuric acid, fuming sulfuricacid, sulfur trioxide, chlorosulfuric acid, fluorosulfuric acid,sulfonic acids such as sulfamic acid, ozone and a combination of aplurality of these oxidizing agents.

Examples of the basic compound of the organic acid anion constitutingthe organic acid anion iron(III) salt include an organic sulfonic acid,an organic carboxylic acid, an organic phosphoric acid and an organicboric acid. Specific examples of the organic sulfonic acid includebenzenesulfonic acid, p-toluenesulfonic acid, methanesulfonic acid,ethanesulfonic acid, α-sulfo-naphthalene, β-sulfo-naphthalene,naphthalenedisulfonic acid and alkylnaphthalenesulfonic acid (examplesof the alkyl group include butyl, triisopropyl and di-t-butyl).

Specific examples of the organic carboxylic acid include acetic acid,propionic acid, benzoic acid and oxalic acid. Furthermore,polyelectrolyte anions such as polyacrylic acid, polymethacrylic acid,polystyrenesulfonic acid, polyvinylsulfonic acid, polyvinylsulfuricacid, poly-α-methylsulfonic acid, polyethylenesulfonic acid andpolyphosphoric acid may be used. These are set forth only for thepurpose of illustrating examples and the organic sulfonic acid or theorganic carboxylic acid of the present invention is by no means limitedthereto.

Examples of the counter anion of the above-described anion include H⁺,alkali metal ions such as Na⁺ and K⁺, and ammonium ions substituted by ahydrogen atom, a tetramethyl group, a tetraethyl group, a tetrabutylgroup or a tetraphenyl group, however, the counter anion is notparticularly limited in the present invention. Among those oxidizingagents, oxidizing agents containing a trivalent Fe-type compound, acuprous chloride-type compound, an alkali persulfate, an ammoniumpersulfate, a manganic acid or a quinone are preferred.

The solution of the oxidizing agent having a polymerization initiatingability may have any concentration as far as the polymerization can takeplace, but preferably has a high concentration. The solution is morepreferably a saturated or supersaturated solution. With respect to themethod of using the solution as a saturated or supersaturated solution,a temperature slightly higher than the reaction temperature is used.Although the temperature may vary depending on the temperaturedependency of the warm solubility of the oxidizing agent, when thetemperature dependency is large, a small temperature difference is usedand when the temperature dependency is small, a large temperaturedifference is used. For example, the oxidizing agent is dissolved in asolvent such as water or alcohol with vigorous stirring at a temperaturefrom a few degree to about 20° C. higher than the polymerizationtemperature and the supernatant of the oxidizing solution is taken out,placed in a reaction vessel and set to a predetermined temperature lowerthan the temperature at the dissolution. Then, a polymerizable monomeror a solution thereof is calmly supplied to the upper surface of theoxidizing agent solution so that mixing of these two solutions can beprevented as much as possible and an interface can be formedtherebetween.

The reaction proceeds at the interface between the two solutions and ahighly electroconductive polymer is produced. The polymer is separatedfrom the reaction solution by evaporation, decantation or the like andwashed. As a result, a highly electroconductive polymer is obtained as amacroscopically scaly material. This may be used as a product highlyelectroconductive polymer after thorough washing. Alternatively, on thepolymer produced which is washed or not washed, a solution of anoxidizing agent having a polymerization initiating ability may be againcontacted with a polymerizable monomer or a solution containing apolymerizable monomer. By repeating this process two or more times,highly electroconductive polymer layers may be stacked.

Also in this case, the solution of the oxidizing agent may have anyconcentration as far as the polymerization can proceed but preferablyhas a high concentration. A saturated or supersaturated solution is morepreferred.

The method for preparing the saturated or supersaturated conditions ofthe oxidizing agent having a polymerization initiating ability on adielectric film layer is not limited particularly. It may be a method inwhich a high concentration solution of the oxidizing agent as it is isintroduced into the pores of a foil or a method in which a lowconcentration solution is introduced in the pores of a foil in advanceso that impregnation occurs sufficiently and dried by leaving it tostand or by heating to induce saturated or supersaturated conditions.

In the production method of a highly electroconductive polymer of thepresent invention, the oxidizing agent anion (reductant of the oxidizingagent) yielded from the oxidizing agent acts as a dopant, therefore, adoping step may be dispensed with. The reductant and another electrolytehaving a doping action are preferably used in combination by allowingthe electrolyte to be present at the polymerization.

Examples of the electrolyte having a doping action which is if desiredallowed to be present together in the production of a polymercomposition for use in the present invention include electrolytecompounds having an oxidizing agent anion (reductant of oxidizing agent)produced from the above-described oxidizing agent as the counter anion,and other anionic electrolytes.

Specific examples thereof include Group 5B element halide anions such asPF₆ ⁻, SbF₆ ⁻ and AsF₆ ⁻, Group 3B element halide anions such as BF₄ ⁻,halogen anions such as I⁻(I₃ ⁻), Br⁻ and Cl⁻, halogen acid anions suchas ClO₄ ⁻, Lewis acid anions such as AlCl₄ ⁻, FeCl₄ ⁻ and SnCl₅ ⁻, andprotonic acid anions such as inorganic acid anion (e.g., NO₃ ⁻, SO₄ ²⁻),organic sulfonic acid anion (e.g., p-toluenesulfonic acid,naphthalenesulfonic acid, naphthalenesulfonic acid substituted withalkyl group having from 1 to 5 carbon atoms, anthraquinonesulfonic acid,CF₃SO₃ ⁻, CH₃SO₃ ⁻) and carboxylic acid anion (e.g., CF₃COO⁻, C₆H₅COO⁻).

Furthermore, polyelectrolyte anions such as polyacrylic acid,polymethacrylic acid, polystyrenesulfonic acid, polyvinylsulfonic acid,polyvinylsulfuric acid, poly-α-methylsulfonic acid, polyethylenesulfonicacid and polyphosphoric acid may be used but the present invention is byno means limited thereto. Among these, high molecular or low molecularorganic sulfonic acid compounds and polyphosphoric acids are preferred,and aromatic sulfonic acid compounds are more preferred.

The concentration of the polymerizable monomer represented by one of thegeneral formulae (6) to (10) above for use in the production of theelectroconductive polymer of the present invention varies depending onthe kind of the substituent of the compound, the kind of the solvent,the kind of another monomer which may be copolymerized or the amountthereof, but, in general, it is preferably from 10⁻³ to 10 mol/L, morepreferably from 10⁻² to 5 mol/L.

The reaction temperature varies depending on the kind of monomer,solvent or oxidizing agent and the reaction method and cannot bespecifically limited but it is preferably a temperature capable ofmaintaining the oxidizing agent in the saturated state at the initiationof polymerization. After the initiation of polymerization, the solventis evaporated and the oxidizing agent precipitates as a solid. In thiscase, when the polymerizable monomer is present as a liquid phase, theinterface of the polymerization system is maintained and thepolymerization continuously proceeds. The reaction temperature isgenerally from −70 to 250° C., preferably from 0 to 150° C., morepreferably from 15 to 100° C.

The reaction solvent for use in the production method of the presentinvention may be any solvent as far as the monomer, the oxidizing agentand the electrolyte having a doping action can dissolve therein togetheror individually. Examples thereof include ethers such as tetrahydrofuran(THF), dioxane and diethyl ether, aprotic polar solvents such asdimethylformamide, acetonitrile, benzonitrile, N-methylpyrrolidone (NMP)and dimethylsulfoxide (DMSO), esters such as ethyl acetate and butylacetate, non-aromatic chlorine-type solvents such as chloroform andmethylene chloride, nitro compounds such as nitromethane, nitroethaneand nitrobenzene, alcohols such as methanol, ethanol and propanol,organic acids such as formic acid, acetic acid and propionic acid, acidan hydrides of the organic acid (e.g., acetic acid anhydride), water,and a mixed solvent thereof. Furthermore, a two-liquid or three-liquidsystem where the oxidizing agent and/or the electrolyte having a dopingaction and the monomer are individually dissolved may also be used.

The highly electroconductive polymers containing the chemical structuresrepresented by the general formulae (1) to (5) and having a fibrilstructure can be obtained from the polymerizable monomers represented bythe general formulae (6) to (10), respectively.

The thus-obtained electroconductive polymer has a very highelectroconductivity which is 10 to 1,000 folds higher than that of theelectroconductive polymer obtained by producing in a reaction system ofan oxidizing agent having a polymerization initiating ability and apolymerizable monomer in a stirring state, more specifically it has anelectroconductivity in the range of from about 0.1 to about 200 S/cm,and in the preferred conditions, the electroconductivity is from 1 to100 S/cm, more preferably from 10 to 100 S/cm.

The thus-produced electroconductive polymer layer as a solidelectrolytic layer of a solid electrolytic capacitor usually can have athickness as small as from 0.1 to 0.3 μm by a single polymerizationstep. Therefore, on the surface (at a porous valve-acting metal) of theelectroconductive polymer having a fibril structure obtained bycontacting the polymerizable monomer with the oxidizing agent having apolymerization initiating ability to produce an electroconductivepolymer and washing or not washing the polymer, the same operation ispreferably performed at least about 3 times, practically 5 times ormore, thereby synthesizing solid polymers. However, it is not preferredthat the solid electrolytic layer has a thickness in excess of thethickness required. The thickness required for the solid electrolyticlayer can be usually obtained by repeating the operation about 20 to 25times, preferably approximately from 7 to 25 times.

On the thus-formed electroconductive polymer layer, an electricallyconductive layer is preferably provided so as to attain good electricalcontact with the cathode lead terminal. The electrically conductivelayer is provided, for example, by solidifying or plating anelectroconductive paste, vaporizing a metal or forming anelectroconductive resin film. Thereafter, a cathode lead terminal isconnected and the capacitor is jacketed with a resin mold, a resin caseor a metal-made jacket case or by resin dipping, then, a solidelectrolytic capacitor for various uses can be obtained.

In the solid electrolytic capacitor of the present invention, a highlyelectroconductive polymer in the fibril structure as a solid electrolyteon the electrode covers the oxide layer within the pores of a porousvalve-acting metal foil subjected to chemical forming, a fibril layerstructure is formed inside the cathode and on the outer surface of themetal foil by repeating the polymerization multiple times, and voidspaces partially remain between adjacent layers, therefore, the thermalstress can be effectively mitigated against rising or falling of thetemperature. Pores are formed also on the surface of theelectroconductive polymer composition, therefore, the electroconductivepaste for connection can enter the pores on the outer surface andthereby good adhesion can be achieved. Furthermore, void spaces areformed also in pores due to the presence of an electroconductive polymerin the fibril structure or by the lamination in a plurality of times,therefore, oxygen is supplied without fail and the recoverability of thedielectric oxide layer at the time of passing electricity is improved.

The polymer having a fibril structure formed on the dielectric film of asolid electrolytic capacitor is of the shape preferably having an outerdiameter in the range of about 3 nm to about 100 nm, more preferably inthe range of about 5 nm to about 50 nm.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereafter, the present invention will be described in greater detail byway of examples and comparative examples. However, these should not beconstrued as limiting the scope of the present invention.

EXAMPLE 1

An aluminum foil chemical formed by etching was cut into a size of 3mm×10 mm and a polyimide solution was coated in a width of 1 mm on bothsurfaces so as to occupy the middle portion of the 10-mm surface andthereby divide the surface into a 4-mm moiety and a 5-mm moiety, anddried to form a masking. The 3 mm×4 mm moiety of the aluminum foilchemical formed by etching was subjected to a chemical forming treatmentwith a 10 wt % aqueous ammonium adipate solution while applying theretoa voltage of 13 V to form a dielectric oxide layer.

Thereafter, this 3 mm×4 mm moiety of aluminum foil was immersed in 2mol/L of an aqueous ammonium persulfate solution (Solution 1), pulled upand then dried at room temperature for 3 minutes. Subsequently, the 3mm×4 mm moiety of aluminum foil was immersed in 1 mol/L of anisopropanol solution of 3,4-ethylenedioxythiophene (Solution 2), pulledup and then left standing in an atmosphere of 40° C. for 10 minutes,thereby performing oxidative polymerization. The operation from theimmersing in Solution 1 and then in Solution 2 until the oxidativepolymerization was performed was repeated 20 times. Thereafter, thealuminum foil was washed with warm water at 50° C. for 10 minutes andthen dried at 100° C. for 30 minutes to form an electroconductivepolymer layer.

FIG. 1 is a photograph (cross section of aluminum foil) by scanningelectron microscopy at a 50,000 magnification of the electroconductivepolymer layer obtained in this Example. FIG. 2 is a photograph (crosssection of aluminum foil) by scanning electron microscopy at a 50,000magnification of the aluminum foil subjected to the chemical formingtreatment.

Also referring to FIG. 2 for comparison, it can be seen that in the FIG.1, (a) shows the aluminum metal moiety of the fine structure, (b) showsthe oxidized alumina dielectric moiety, and (c) shows the fibrillarelectroconductive polymers deposited on the surface of the dielectricmoiety assembling in a cluster (in FIG. 1, the fibrils look like anetwork patterned film), and that the electroconductive polymer film hada thickness of about 0.06 μm. The observation of FIG. 1 reveals that theouter diameter of the fibril is approximately 5 to 50 nm. The structureof fibrillar electroconductive polymer (film-like) moiety (c) has astructure similar to that of the highly electroconductive polymerobtained by reacting “3,4-ethylenedioxythiophene” and “polymerizationinitiator (containing an oxidizing agent)” at an interface as describedin Examples 14 and 15.

On the portion having formed thereon an electroconductive polymer layerof the aluminum foil, carbon paste and silver paste were coated. Foursheets of the aluminum foils were stacked, a cathode lead terminal wasconnected, and an anode lead terminal was connected by welding to thealuminum foil portion where the electroconductive polymer layer was notformed. Thereafter, this element was sealed by epoxy resin and then agedat 125° C. for 2 hours while applying thereto a rated voltage. Throughsuch an operation, 30 capacitors in total were completed.

These 30 capacitor elements were measured on the capacity, loss factor(tan δ) at 120 Hz, and the impedance at a resonance frequency and theleakage current as the initial evaluation. The leakage current wasmeasured one minute after the rated voltage was applied. The average ofrespective measured values, the defective ratio when the leakage currentof 0.16 μA (0.002 CV) or more was judged as a defective, and the numberof short circuited products are shown in Table 1.

With respect to the leakage current, the average is a value calculatedexcluding the defectives. The results in the reflow test and themoisture resistance test subsequent thereto are shown in Table 2. In themoisture resistance test, a leakage current of 3.2 μA (0.04 CV) or morewas judged as a defective. The reflow test (also referred to assoldering heat resistance test) was performed by the following method.That is, 30 capacitors were provided and the capacitors were traveledthrough the zone at a temperature of 230° C. over 30 seconds.Thereafter, the leakage current after one minute from applying the ratedcurrent was measured and the leakage current of 0.04 CV (3.2 μA) or morewas judged as a defective. In the moisture resistance test, thecapacitor was left standing at a high temperature and high humidity of85° C. and 85% RH for 500 hours.

EXAMPLE 2

30 Capacitors were completed in the same manner as in Example 1 exceptfor using ferric sulfate in place of ammonium persulfate, usingdihydroisothianaphthene in place of 3,4-ethylenedioxythiophene andchanging the polymerization temperature to 60° C. in Example 1. Thesecapacitor elements were evaluated on the properties in the same manneras in Example 1. The results obtained are shown in Tables 1 and 2.

EXAMPLE 3

30 Capacitors were completed in the same manner as in Example 1 exceptfor using pyrrole in place of 3,4-ethylenedioxythiophene in Example 1.These capacitor elements were evaluated on the properties in the samemanner as in Example 1. The results obtained are shown in Tables 1 and2.

EXAMPLE 4

30 Capacitors were completed in the same manner as in Example 1 exceptfor using aniline in place of 3,4-ethylenedioxythiophene in Example 1.These capacitor elements were evaluated on the properties in the samemanner as in Example 1. The results obtained are shown in Tables 1 and2.

EXAMPLE 5

30 Capacitors were completed in the same manner as in Example 1 exceptthat sodium anthraquinone-2-sulfonate as a compound having a dopingaction was added to 2 mol/L of an aqueous ammonium persulfate solutionto have a concentration of 0.07 mol/L in Example 1. These capacitorelements were evaluated on the properties in the same manner as inExample 1. The results obtained are shown in Tables 1 and 2.

EXAMPLE 6

30 Capacitors were completed in the same manner as in Example 1 exceptfor changing the concentration of the isopropanol solution of3,4-ethylenedioxythiophene to 5 mol/L in Example 1. These capacitorelements were evaluated on the properties in the same manner as inExample 1. The results obtained are shown in Tables 1 and 2.

EXAMPLE 7

30 Capacitors were completed in the same manner as in Example 1 exceptfor changing the concentration of the isopropanol solution of3,4-ethylenedioxythiophene to 0.01 mol/L in Example 1. These capacitorelements were evaluated on the properties in the same manner as inExample 1. The results obtained are shown in Tables 1 and 2.

EXAMPLE 8

30 Capacitors were completed in the same manner as in Example 1 exceptfor using 0.07 mol/L of sodium 6-methoxynaphthalenesulfonate in place of0.07 mol/L of sodium anthraquinone-2-sulfonate in Example 5. Thesecapacitor elements were evaluated on the properties in the same manneras in Example 1. The results obtained are shown in Tables 1 and 2.

EXAMPLE 9

30 Capacitors were completed in the same manner as in Example 1 exceptfor changing the concentration of the aqueous ammonium persulfatesolution to 0.01 mol/L in Example 1. These capacitor elements wereevaluated on the properties in the same manner as in Example 1. Theresults obtained are shown in Tables 1 and 2.

EXAMPLE 10

30 Capacitors were completed in the same manner as in Example 1 exceptfor changing the concentration of the aqueous ammonium persulfatesolution to 4 mol/L in Example 1. These capacitor elements wereevaluated on the properties in the same manner as in Example 1. Theresults obtained are shown in Tables 1 and 2.

EXAMPLE 11

30 Capacitors were completed in the same manner as in Example 1 exceptfor repeating the operation from the immersing in Solution 1 until theoxidation polymerization was performed two times in Example 1. Thesecapacitor elements were evaluated on the properties in the same manneras in Example 1. The results obtained are shown in Tables 1 and 2.

EXAMPLE 12

30 Capacitors were completed in the same manner as in Example 1 exceptfor using furan in place of 3,4-ethylenedioxythiophene and using 1.4mol/L of iron (III) paratoluenesulfonate hexahydrate in place of 2 mol/Lof ammonium persulfate. These capacitor elements were evaluated on theproperties in the same manner as in Example 1. The results obtained areshown in Tables 1 and 2. The electroconductive polymer layer obtained inthis Example was observed by scanning electron microscopy under the sameconditions as in Example 1. As a result, the morphology similar to thatshown in FIG. 1 was observed.

COMPARATIVE EXAMPLE 1

30 Capacitor were completed in the same manner as in Example 1 exceptthat referring to JP-A-10-50558, a polymer was formed by once dipping analuminum foil in a chemical polymerization solution having dissolvedtherein 2.87 g (0.02 mol) of 3,4-ethylenedioxythiphene and 29.8 g (0.044mol) of iron (III) paratoluenesulfonate hexahydrate, heat treating thisat 100° C. to form a polymer on the foil, and applying anelectroconductive paste (carbon and silver powder) to the portion wherethe electroconductive polymer layer was formed. These capacitor elementswere evaluated on the properties in the same manner as in Example 1. Theresults obtained are shown in Tables 1 and 2.

TABLE 1 Initial Properties Number of Capac- Loss Imped- Leakage Defec-Short ity Factor ance Current tive Circuited (μF) (%) (mΩ) (μA) RatioCapacitors Example 1 48.7 0.7 12 0.03 0/30 0 Example 2 47.9 0.9 14 0.050/30 0 Example 3 48.6 0.8 13 0.06 0/30 0 Example 4 48.3 0.8 17 0.07 0/300 Example 5 48.1 0.9 13 0.09 0/30 0 Example 6 48.8 1.0 11 0.07 0/30 0Example 7 47.6 1.1 18 0.07 0/30 0 Example 8 48.2 0.9 16 0.08 0/30 0Example 9 47.9 1.2 21 0.08 0/30 0 Example 10 48.3 0.9 14 0.10 0/30 0Example 11 47.8 1.3 24 0.13 0/30 0 Example 12 48.2 0.9 18 0.06 0/30 0Compara- 47.9 2.2 80 0.17 2/30 2 tive Example 1

TABLE 2 Reflow Test Moisture Resistance Test Number of Number of ShortLeakage Short Defective Circuited Current Defective Circuited RatioCapacitors (μA) Ratio Capacitors Example 1 0/30 0 0.49 0/30 0 Example 20/30 0 0.54 0/30 0 Example 3 0/30 0 0.59 0/30 0 Example 4 0/30 0 0.570/30 0 Example 5 0/30 0 0.61 0/30 0 Example 6 0/30 0 0.61 0/30 0 Example7 0/30 0 0.55 0/30 0 Example 8 0/30 0 0.56 0/30 0 Example 9 0/30 0 0.420/30 0 Example 10 0/30 0 0.68 0/30 0 Example 11 0/30 0 0.69 0/30 0Example 12 0/30 0 0.60 0/30 0 Comparative 3/27 3 1.68 5/27 3 Example 1

EXAMPLE 13

6.49 g (0.04 mol) of ferric chloride was put in a 30 ml-volume sampletube and 8 ml of water was charged thereinto to prepare an aqueousferric chloride solution. Into this solution, 1.68 g (0.02 mol) ofthiophene as a polymerizable monomer was calmly poured. The thiopheneassumed an upper layer and an interface was generated therebetween. Thesample tube was dipped in a warm bath at 40° C. to initiate thepolymerization. After 2 hours, the heating was stopped, the sample tubewas taken out, and the polymerized product was collected by filtration.To this solid content, 100 ml of water was added, and the resultingsolution was stirred for 1 hour and filtered to remove by dissolvingexcess ferric chloride. Subsequently, 100 ml of acetone was added to theresidue, and the mixture was stirred for 1 hour and then filtered toremove unreacted thiophene and soluble low molecular polymer. After thisprocess, a purified polymer was obtained. Thereafter, the purifiedpolymer was dried in vacuo at room temperature for a whole day andnight, then the polymer of pellets each having a radius of 1 cm wasprepared in a vacuum while continuously applying a pressure of 10 t for3 minutes. Using Loresta IP MCP-250 (manufactured by MitsubishiPetrochemical Co., Ltd.), the surface resistance of the pellet wasmeasured and from the surface resistance obtained, theelectroconductivity was calculated and found to be 16 S/cm.

COMPARATIVE EXAMPLE 2

6.49 g (0.04 mol) of ferric chloride was put in a 100 ml-volumeround-bottom-flask containing a stirring piece and 16 ml of water wascharged thereinto to completely dissolve the ferric chloride. The flaskwas dipped in a warm bath at 40° C. Then, 1.68 g (0.02 mol) of thiopheneas a polymerizable monomer was heated at 30° C., dissolved in 24 ml ofisopropanol and introduced into the reaction system, and the stirringwas started. During the polymerization reaction, the stirring wascontinued all the time. After 2 hours, the heating was stopped, thesample tube was taken out, and the polymerized product was collected byfiltration. To this solid content, 100 ml of water was added, and theresulting solution was stirred for 1 hour and filtered to remove bydissolving excess ferric chloride. Subsequently, 100 ml of acetone wasadded to the residue, and the mixture was stirred for 1 hour and thenfiltered to remove unreacted thiophene and soluble low molecularpolymer. After this process, a purified polymer was obtained.

Thereafter, the purified polymer was dried in vacuo at room temperaturefor a whole day and night and dried. The polymer obtained was finepowder. This polymer was formed in a vacuum while continuously applyinga pressure of 10 t for 3 minutes to prepare pellets each having a radiusof 1 cm. Using Loresta IP MCP-250 (manufactured by MitsubishiPetrochemical Co., Ltd.), the surface resistance of the pellet wasmeasured and from the surface resistance obtained, theelectroconductivity was calculated and found to be 0.0054 S/cm.

EXAMPLE 14

6.85 g (0.03 mol) of ammonium persulfate was put in a 30 ml-volumesample tube and 8 ml of water was charged thereinto to prepare asolution. Into this solution, 2.87 g (0.02 mol) of3,4-ethylenedioxythiophene as a polymerizable monomer was calmly poured.An interface was generated between the 3,4-ethylenedioxythiophene andthe aqueous solution. The sample tube was dipped in a warm bath at 40°C. to initiate the polymerization. The polymerization proceeding at theinterface formed by the aqueous solution containing the oxidizing agentand the 3,4-ethylenedioxythiophene was observed. After 2 hours, theheating was stopped, the sample tube was taken out, and the polymerizedproduct was collected by filtration. To this solid content, 100 ml ofwater was added, the resulting solution was stirred for 1 hour andfiltered to remove by dissolving excess ammonium persulfate.Subsequently, 100 ml of acetone was added to the residue, and themixture was stirred for 1 hour and then filtered to remove unreacted3,4-ethylenedioxythiophene and soluble low molecular polymer. After thisprocess, a purified polymer was obtained.

FIG. 3 is an SEM photograph at a 5,100 magnification of the purifiedpolymer. FIG. 4 is an enlarged SEM photograph at a 50,000 magnificationof the fibril structure moiety of FIG. 3. In FIG. 4, the fibrilstructure is clearly seen. The observation of FIG. 4 revealed that thefibril had an outer diameter of approximately 10 to 60 nm.

Thereafter, the purified polymer was dried in vacuo at room temperaturefor a whole day and night, then the polymer of pellets each having aradius of 1 cm was prepared in a vacuum while continuously applying apressure of 10 t for 3 minutes. Using Loresta IP MCP-250 (manufacturedby Mitsubishi Petrochemical Co., Ltd.), the surface resistance of thepellet was measured and from the surface resistance obtained, theelectroconductivity was calculated and found to be 20 S/cm.

COMPARATIVE EXAMPLE 3

This Example was performed in the same manner as in Comparative Example2 except for using 2.87 g (0.02 mol) of 3,4-ethylenedioxythiophene as apolymerizable monomer and 6.85 g (0.03 mol) of ammonium persulfate as apolymerization oxidizing agent.

FIG. 5 is an enlarged SEM photograph at a 50,000 magnification of thepurified polymer. The fibril structure was not observed.

Thereafter, the purified polymer was dried in vacuo at room temperaturefor a whole day and night, then the polymer of pellets each having aradius of 1 cm was prepared in a vacuum while continuously applying apressure of 10 t for 3 minutes. Using Loresta IP MCP-250 (manufacturedby Mitsubishi Petrochemical Co., Ltd.), the surface resistance of thepellet was measured and from the surface resistance obtained, theelectroconductivity was calculated and found to be 0.064 S/cm.

EXAMPLE 15

6.85 g (0.03 mol) of ammonium persulfate was put in a 30 ml-volumesample tube and 1 ml of water was charged thereinto to prepare asaturated solution containing undissolved ammonium persulfate. Into thissolution, 2.87 g (0.02 mol) of 3,4-ethylenedioxythiophene as apolymerizable monomer was calmly poured. The sample tube was dipped in awarm bath at 40° C. to initiate the polymerization in an open system.After 2 hours, the heating was stopped, the sample tube was taken out,and the polymerized product was collected by filtration. To this solidcontent, 100 ml of water was added, and the resulting solution wasstirred for 1 hour to remove the excess of ammonium persulfate. Then,the solid was filtered. Subsequently, 100 ml of acetone was added to theresidue, and the mixture was stirred for 1 hour and then filtered toremove unreacted 3,4-ethylenedioxythiophene and soluble low molecularpolymer. After this process, a purified polymer was obtained.

FIG. 6 is an enlarged SEM photograph at a 2,000 magnification of thepurified polymer. FIG. 7 is an enlarged SEM photograph at a 20,000magnification of the fibril structure moiety of FIG. 6. The fibrilstructure is clearly seen.

Thereafter, the purified polymer was dried in vacuo at room temperaturefor a whole day and night, then the polymer of pellets each having aradius of 1 cm was prepared in a vacuum while continuously applying apressure of 10 t for 3 minutes. Using Loresta IP MCP-250 (manufacturedby Mitsubishi Petrochemical Co., Ltd.), the surface resistance of thepellet was measured and from the surface resistance obtained, theelectroconductivity was calculated and found to be 21 S/cm.

EXAMPLE 16

6.85 g (0.03 mol) of ammonium persulfate was put in a 30 ml-volumesample tube and 8 ml of water was charged thereinto to prepare asolution. Into this solution, 1.86 g (0.014 mol) of1,3-dihydroisothianaphthene as a polymerizable monomer heated at 30° C.was calmly poured so that an interface could be generated between themonomer and the oxidizing agent solution. The sample tube was dipped ina warm bath at 40° C. to initiate the polymerization. After 6 hours, theheating was stopped, the sample tube was allowed to stand for 7 days tocomplete the reaction and then taken out, and the polymerized productwas collected by filtration. To this solid content, 100 ml of water wasadded, and the resulting solution was stirred for 1 hour and filtered toremove by dissolving the excess of ammonium persulfate. Subsequently,100 ml of acetone was added to the residue, and the mixture was stirredfor 1 hour and then filtered to remove unreacted1,3-dihydroisothianaphthene and soluble low molecular polymer. Afterthis process, a purified polymer was obtained.

FIG. 8 is an enlarged SEM (scanning electron microscope) photograph at a50,000 magnification of the purified polymer. The fibril structure isclearly seen. The observation of FIG. 8 revealed that the fibril had anouter diameter of approximately 10 to 50 nm.

Thereafter, the purified polymer was dried in vacuo at room temperaturefor a whole day and night, then the polymer of pellets each having aradius of 1 cm was prepared in a vacuum while continuously applying apressure of 10 t for 3 minutes. Using Loresta IP MCP-250 (manufacturedby Mitsubishi Petrochemical Co., Ltd.), the surface resistance of thepellet was measured and from the surface resistance obtained, theelectroconductivity was calculated and found to be 14 S/cm.

COMPARATIVE EXAMPLE 4

This Comparative Example was performed in the same manner as inComparative Example 2 except for using 1.86 g (0.014 mol) of1,3-dihydroisothianaphthene as a polymerizable monomer and changing thepolymerization time to 2 hours. The polymer obtained was dried andformed in a vacuum while continuously applying a pressure of 10 t for 3minutes to prepare pellets each having a radius of 1 cm. Using LorestaIP MCP-250 (manufactured by Mitsubishi Petrochemical Co., Ltd.), thesurface resistance of the pellet was measured and from the surfaceresistance obtained, the electroconductivity was calculated and found tobe 0.0033 S/cm.

FIG. 9 is an enlarged SEM photograph at a 50,000 magnification of thepolymer obtained. The fibril structure was not observed.

EXAMPLE 17

6.85 g (0.03 mol) of ammonium persulfate was put in a 30 ml-volumesample tube and 8 ml of 0.1N—HCl aqueous solution was charged thereintoto prepare a solution. Into this solution, 1.86 g (0.02 mol) of anilineas a polymerizable monomer was calmly poured. The sample tube was dippedin a warm bath at 40° C. to initiate the polymerization. After 2 hours,the heating was stopped, the sample tube then taken out, and thepolymerized product was collected by filtration. To this solid content,100 ml of water was added, and the resulting solution was stirred for 1hour and filtered to remove by dissolving the excess of ammoniumpersulfate. Subsequently, 100 ml of acetone was added to the residue,and the mixture was stirred for 1 hour and then filtered to removeunreacted aniline and soluble low molecular polymer. After this process,a purified polymer was obtained. Thereafter, the purified polymer wasdried in vacuo at room temperature for a whole day and night, then thepolymer of pellets each having a radius of 1 cm was prepared in a vacuumwhile continuously applying a pressure of 10 t for 3 minutes. UsingLoresta IP MCP-250 (manufactured by Mitsubishi Petrochemical Co., Ltd.),the surface resistance of the pellet was measured and from the surfaceresistance obtained, the electroconductivity was calculated and found tobe 10 S/cm.

COMPARATIVE EXAMPLE 5

This Comparative Example was performed in the same manner as inComparative Example 3 except for using 1.86 g (0.02 mol) of aniline as apolymerizable monomer. The polymer obtained was dried and formed in avacuum while continuously applying a pressure of 10 t for 3 minutes toprepare pellets each having a radius of 1 cm. Using Loresta IP MCP-250(manufactured by Mitsubishi Petrochemical Co., Ltd.), the surfaceresistance of the pellet was measured and from the surface resistanceobtained, the electroconductivity was calculated and found to be 0.0024S/cm.

EXAMPLE 18

6.85 g(0.03mol) of ammonium persulfate and 0.46 g (0.0014 mol) of sodiumanthraquinone-2-sulfonate were put in a 30 ml-volume sample tube and 8ml of water was charged thereinto to prepare a solution. Into thissolution, 2.87 g (0.02 mol) of 3,4-ethylenedioxythiophene as apolymerizable monomer was calmly poured. The sample tube was dipped in awarm bath at 40° C. to initiate the polymerization. After 2 hours, theheating was stopped, the sample tube then taken out, and the polymerizedproduct was collected by filtration. To this solid content, 100 ml ofwater was added, and the resulting solution was stirred for 1 hour andfiltered to remove by dissolving the excess of ammonium persulfate andthe excess of sodium anthraquinone-2-sulfonate. Subsequently, 100 ml ofacetone was added to the residue, and the mixture was stirred for 1 hourand then filtered to remove unreacted 3,4-ethylenedioxythiophene andsoluble low molecular polymer. After this process, a purified polymerwas obtained. Thereafter, the purified polymer was dried in vacuo atroom temperature for a whole day and night, then the polymer of pelletseach having a radius of 1 cm was prepared in a vacuum while continuouslyapplying a pressure of 10 t for 3 minutes. Using Loresta IP MCP-250(manufactured by Mitsubishi Petrochemical Co., Ltd.), the surfaceresistance of the pellet was measured and from the surface resistanceobtained, the electroconductivity was calculated and found to be 26S/cm.

EXAMPLE 19

6.85 g (0.03 mol) of ammonium persulfate was put in a 30 ml-volumesample tube and 8 ml of water was charged thereinto to prepare asolution. Into this solution, 2.87 g (0.02 mol) of3,4-ethylenedioxythiophene as a polymerizable monomer was calmly poured.The sample tube was dipped in a warm bath at 40° C. to initiate thepolymerization. After 2 hours, the heating was stopped, the sample tubethen taken out, and the polymerized product was collected by filtration.Again, 6.85 g (0.03 mol) of ammonium persulfate was sampled in a 30ml-volume sample tube and 8 ml of water was charged thereinto to preparea solution. Into this solution, 2.87 g (0.02 mol) of3,4-ethylenedioxythiophene as a polymerizable monomer was calmly poured.The polymerized product taken out above was placed in the system, andthe sample tube was dipped in a warm bath at 40° C. to initiate thepolymerization. This process was repeated 3 times to stack the polymerlayers. To the solid content obtained, 100 ml of water was added, andthe resulting solution was stirred for 1 hour and filtered to remove bydissolving the excess of ammonium persulfate. Subsequently, 100 ml ofacetone was added to the residue, and the mixture was stirred for 1 hourand then filtered to remove unreacted 3,4-ethylenedioxythiophene andsoluble low molecular polymer. After this process, a purified polymerwas obtained. Thereafter, the purified polymer was dried in vacuo atroom temperature for a whole day and night, then the polymer of pelletseach having a radius of 1 cm was prepared in a vacuum while continuouslyapplying a pressure of 10 t for 3 minutes. Using Loresta IP MCP-250(manufactured by Mitsubishi Petrochemical Co., Ltd.), the surfaceresistance of the pellet was measured and from the surface resistanceobtained, the electroconductivity was calculated and found to be 29S/cm.

EXAMPLE 20

27.10 g (0.04 mol) of iron (III) paratoluenesulfonate hexahydrate wasput in a 30 ml-volume sample tube and 8 ml of water was chargedthereinto to prepare an aqueous oxidizing agent solution. Into thissolution, 1.36 g (0.02 mol) of furan as a polymerizable monomer wascalmly poured. Furan formed an upper layer of the aqueous solution togenerate an interface between furan and the aqueous solution. The sampletube was dipped in a warm bath at 40° C. to initiate the polymerization.After 2 hours, the heating was stopped, the sample tube then taken out,and the polymerized product was collected by filtration. To the solidcontent obtained, 100 ml of water was added, and the resulting solutionwas stirred for 1 hour and filtered to remove by dissolving the excessof iron (III) paratoluenesulfonate hexahydrate. Subsequently, 100 ml ofacetone was added to the residue, and the mixture was stirred for 1 hourand then filtered to remove unreacted furan and soluble low molecularpolymer. After this process, a purified polymer was obtained.Thereafter, the purified polymer was dried in vacuo at room temperaturefor a whole day and night, then the polymer of pellets each having aradius of 1 cm was prepared in a vacuum while continuously applying apressure of 10 t for 3 minutes. Using Loresta IP MCP-250 (manufacturedby Mitsubishi Petrochemical Co., Ltd.), the surface resistance of thepellet was measured and from the surface resistance obtained, theelectroconductivity was calculated and found to be 13 S/cm.

The electroconductive polymer layer obtained in this Example wasobserved by scanning electron microscopy under the same conditions as inExample 14. As a result, the morphology similar to that shown in FIGS. 3and 4 was observed.

EXAMPLE 21

6.49 g (0.04 mol) of ferric chloride was put in a 30 ml-volume sampletube and 8 ml of water was charged thereinto to prepare an aqueousferric chloride solution. Into this solution, 1.34 g (0.02 mol) ofpyrrole as a polymerizable monomer was calmly poured. Pyrrole formed anupper layer of the aqueous solution to generate an interface betweenpyrrole and the aqueous solution. The sample tube was dipped in a warmbath at 40° C. to initiate the polymerization. After 2 hours, theheating was stopped, the sample tube then taken out, and the polymerizedproduct was collected by filtration. To the solid content obtained, 100ml of water was added, and the resulting solution was stirred for 1 hourand filtered to remove by dissolving the excess of ferric chloride.Subsequently, 100 ml of acetone was added to the residue, and themixture was stirred for 1 hour and then filtered to remove unreactedpyrrole and soluble low molecular polymer. After this process, apurified polymer was obtained. Thereafter, the purified polymer wasdried in vacuo at room temperature for a whole day and night, then thepolymer of pellets each having a radius of 1 cm was prepared in a vacuumwhile continuously applying a pressure of 10 t for 3 minutes. UsingLoresta IP MCP-250 (manufactured by Mitsubishi Petrochemical Co., Ltd.),the surface resistance of the pellet was measured and from the surfaceresistance obtained, the electroconductivity was calculated and found tobe 21 S/cm.

The electroconductive polymer layer obtained in this Example wasobserved by scanning electron microscopy under the same conditions as inExample 14. As a result, the morphology similar to that shown in FIGS. 3and 4 was observed.

Industrial Applicability

According to the present invention, highly electroconductive film-likepolymer composition containing a repeating unit represented by thegeneral formula (1) to (5) and having a fibril structure, excellentanisotropy and superior film property can be obtained by a simplechemical oxidation polymerization method where a polymerizable monomerrepresented by the general formula (6) to (10) alone or together with anelectrolyte having a doping action is contacted with a solutioncontaining an oxidizing agent having a polymerization initiating abilityand is polymerized at the interface formed. Such a highlyelectroconductive polymer composition is industrially useful for variousapplications as a highly electroconductive solid electrolyte for use ina solid electrolytic capacitor, as an electroconductive material for usein an antistatic material, an electric wave absorbing material, etc.

According to the present invention, in a solid electrolytic capacitorusing an electroconductive polymer as a solid electrolyte, the solidelectrolyte formed on a dielectric film layer is the above polymercomprising a repeating unit represented by the general formula (1), (2),(3), (4) or (5) and having a fibril structure, excellent anisotropy andsuperior film property and therefore, a solid electrolytic layer havingan ability of mitigating the thermal stress and an excellent adhesion tothe paste layer can be obtained.

Furthermore, according to the present invention, the anode is covered bythe above-described solid electrolyte in the film form having a highelectroconductivity such that void spaces remain in the anode pores andtherefore, the solid electrolytic layer obtained can have also excellentfilm recoverability at the time of passing electricity.

By virtue of these effects, a solid electrolytic capacitor having notonly initial properties (e.g., loss factor, leakage current, heatresistance, equivalent series resistance and impedance in the highfrequency region) but also excellent long-term reliability (e.g.,durability at high temperature and high humidity) can be provided.

What is claimed is:
 1. A solid electrolytic capacitor comprising adielectric film layer on a porous valve-acting metal and a solidelectrolytic layer formed on said dielectric film layer, wherein saidsolid electrolytic layer comprises an electroconductive polymer inlayers, said electroconductive polymer having an electroconductivity offrom about 0.1 to about 200 S/cm and having a scaly fibrillar structurewith an outer diameter in the range of about 3 nm to about 100 nm, theelectroconductive polymer layers being formed inside a cathode and onthe outer surface of the metal, void spaces partially remaining betweenadjacent polymer layers.
 2. The solid electrolytic capacitor as claimedin claim 1, wherein said solid polymer electrolytic layer is anelectroconductive polymer having a fibril structure comprising as arepeating unit a structure having a thiophene-diyl skeleton representedby the following general formula (1):

(wherein R¹ and R² each independently represent a monovalent groupselected from the group consisting of a hydrogen atom, a linear orbranched, saturated or unsaturated alkyl, alkoxy or alkyl ester grouphaving from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyanogroup, a primary, secondary or tertiary amino group, a CF₃ group, aphenyl group and a substituted phenyl group, the hydrocarbon chains ofR¹ and R² may combine with each other at any position to form a divalentchain for forming a 3-, 4-, 5-, 6- or 7-membered saturated orunsaturated hydrocarbon cyclic structure together with the carbon atomssubstituted by R¹ and R², the cyclic bonded chain may optionally containa bond such as carbonyl, ether, ester, amide, sulfide, sulfinyl,sulfonyl and imino at any position, δ represents a number in the rangeof from 0 to 1, Z represents an anion, and j represents a valence of Zand is 1 or 2).
 3. The solid electrolytic capacitor as claimed in claim1, wherein said solid polymer electrolytic layer is an electroconductivepolymer having a fibril structure comprising as a repeating unit astructure having a condensed polycyclic skeleton represented by thefollowing general formula (2):

(wherein R³, R⁴, R⁵, R⁶, R⁷ and R⁸ each independently represent amonovalent group selected from the group consisting of a hydrogen atom,a linear or branched, saturated or unsaturated alkyl, alkoxy or alkylester group having from 1 to 10 carbon atoms, a halogen atom, a nitrogroup, a cyano group, a primary, secondary or tertiary amino group, aCF₃ group, a phenyl group and a substituted phenyl group, thehydrocarbon chains of R³, R⁴, R⁵, R⁶, R⁷ or R⁸ may combine with eachother at any position to form a divalent chain for forming at least one3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclicstructure together with the carbon atoms substituted by R³, R⁴, R⁵, R⁶,R⁷ or R⁸, the cyclic bonded chain may optionally contain a bond such ascarbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino atany position, k represents the number of condensed rings surrounded bythe thiophene ring and the benzene ring having the substituents R³ to R⁶and is 0 or an integer of from 1 to 3, the condensed ring in the formulamay contain an optional number of nitrogen or N-oxide, with the provisothat the substituents R³ to R⁸ are deducted by the number of nitrogen orN-oxide, δ represents a number in the range of from 0 to 1, Z representsan anion, and j represents a valence of Z and is 1 or 2).
 4. The solidelectrolytic capacitor as claimed in claim 1, wherein said solid polymerelectrolytic layer is an electroconductive polymer having a fibrilstructure comprising as a repeating unit a structure having apyrrole-diyl skeleton represented by the following general formula (3):

(wherein R⁹ and R¹⁰ each independently represent a monovalent groupselected from the group consisting of a hydrogen atom, a linear orbranched, saturated or unsaturated alkyl, alkoxy or alkyl ester grouphaving from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyanogroup, a primary, secondary or tertiary amino group, a CF₃ group, aphenyl group and a substituted phenyl group, the hydrocarbon chains ofR⁹ and R¹⁰ may combine with each other at an optional position to form adivalent chain for forming at least one 3-, 4-, 5-, 6- or 7-memberedsaturated or unsaturated hydrocarbon cyclic structure together with thecarbon atoms substituted by R⁹ and R¹⁰, and the cyclic bonded chain mayoptionally contain a bond such as carbonyl, ether, ester, amide,sulfide, sulfinyl, sulfonyl and imino at any position, δ represents anumber in the range of from 0 to 1, Z represents an anion, and jrepresents a valence of Z and is 1 or 2).
 5. The solid electrolyticcapacitor as claimed in claim 1, wherein said solid polymer electrolyticlayer is an electroconductive polymer having a fibril structurecomprising as a repeating unit a structure having a furan-diyl skeletonrepresented by the following general formula (4):

(wherein the substituents R¹¹ and R¹² each independently represent amonovalent group selected from the group consisting of a hydrogen atom,a linear or branched, saturated or unsaturated alkyl, alkoxy or alkylester group having from 1 to 10 carbon atoms, a halogen atom, a nitrogroup, a cyano group, a primary, secondary or tertiary amino group, aCF₃ group, a phenyl group and a substituted phenyl group, thehydrocarbon chains of R¹¹ and R¹² may combine with each other at anyposition to form a divalent chain for forming at least one 3-, 4-, 5-,6- or 7-membered saturated or unsaturated hydrocarbon cyclic structuretogether with the carbon atoms substituted by R¹¹ and R¹², the cyclicbonded chain may optionally contain a bond such as carbonyl, ether,ester, amide, sulfide, sulfinyl, sulfonyl and imino at any position, δrepresents a number in the range of from 0 to 1, Z represents an anion,and j represents a valence of Z and is 1 or 2).
 6. The solidelectrolytic capacitor as claimed in claim 1, wherein said solid polymerelectrolytic layer is an electroconductive polymer having a fibrilstructure comprising as a repeating unit a structure having animinophenylene skeleton represented by the following general formula(5):

(wherein the substituents R¹³, R¹⁴, R¹⁵ and R¹⁶ each independentlyrepresent a monovalent group selected from the group consisting of ahydrogen atom, a linear or branched, saturated or unsaturated alkyl,alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogenatom, a nitro group, a cyano group, a primary, secondary or tertiaryamino group, a CF₃ group, a phenyl group and a substituted phenyl group,the hydrocarbon chains of R¹³, R¹⁴, R¹⁵ or R¹⁶ may combine with eachother at any position to form a divalent chain for forming at least one3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclicstructure together with the carbon atoms substituted by R¹³, R¹⁴, R¹⁵ orR¹⁶, the cyclic bonded chain may optionally contain a bond such ascarbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino atany position, δ represents a number in the range of from 0 to 1, Zrepresents an anion, and j represents a valence of Z and is 1 or 2). 7.A method for producing a solid electrolytic capacitor comprising a solidelectrolytic layer composed of a polymer in layers, saidelectroconductive polymer having an electroconductivity of from about0.1 to about 200 S/cm having a scaly fibrillar structure with an outerdiameter in the range of about 3 nm to about 100 nm on a dielectric filmlayer of a porous valve-acting metal, wherein the polymer layers areformed inside a cathode and on the outer surface of the metal, voidspaces partially remaining between adjacent polymer layers, whichcomprises the step of contacting a polymerizable monomer with a singlesolution containing an oxidizing agent having a polymerizationinitiating ability kept in the saturated or supersaturated state or amixed solution containing the oxidizing agent and an electrolyte havinga doping action on said dielectric film, thereby forming a compositionin the form of a film of a polymer having a fibril structure on saiddielectric film.
 8. The method for producing a solid electrolyticcapacitor as claimed in claim 7, which comprises the step of contactingon said dielectric film a polymerizable monomer represented by thefollowing general formula (6):

(wherein R¹ and R² each independently represent a monovalent groupselected from the group consisting of a hydrogen atom, a linear orbranched, saturated or unsaturated alkyl, alkoxy or alkyl ester grouphaving from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyanogroup, a primary, secondary or tertiary amino group, a trihalomethylgroup, a phenyl group and a substituted phenyl group, the hydrocarbonchains of R¹ and R² may combine with each other at any position to forma divalent chain for forming a 3-, 4-, 5-, 6- or 7-membered saturated orunsaturated hydrocarbon cyclic structure together with the carbon atomssubstituted by R¹ and R², the cyclic bonded chain may optionally containa bond such as carbonyl, ether, ester, amide, sulfide, sulfinyl,sulfonyl and imino at any position) with a solution containing anoxidizing agent having a polymerization initiating ability, therebyforming a composition in the form of a film of a polymer having a fibrilstructure on said dielectric film.
 9. The method for producing a solidelectrolytic capacitor as claimed in claim 7, which comprises the stepof contacting on said dielectric film a polymerizable monomerrepresented by the following general formula (7):

(wherein the substituents R³, R⁴, R⁵, R⁶, R⁷ and R⁸ each independentlyrepresent a monovalent group selected from the group consisting of ahydrogen atom, a linear or branched, saturated or unsaturated alkyl,alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogenatom, a nitro group, a cyano group, a primary, secondary or tertiaryamino group, a CF₃ group, a phenyl group and a substituted phenyl group,the hydrocarbon chains of R³, R⁴, R⁵, R⁶, R⁷ or R⁸ may combine with eachother at any position to form a divalent chain for forming at least one3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclicstructure together with the carbon atoms substituted by R³, R⁴, R⁵, R⁶,R⁷ or R⁸, the cyclic bonded chain may optionally contain a bond such ascarbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino atany position, k represents the number of condensed rings surrounded bythe thiophene ring and the benzene ring having the substituents R³ to R⁶and is 0 or an integer of from 1 to 3, the condensed ring in the formulamay contain an optional number of nitrogen or N-oxide, with the provisothat the substituents R³ to R⁸ are deducted by the number of nitrogen orN-oxide) with a solution containing an oxidizing agent having apolymerization initiating ability, thereby forming a composition in theform of a film of a polymer having a fibril structure on said dielectricfilm.
 10. The method for producing a solid electrolytic capacitor asclaimed in claim 7, which comprises the step of contacting on saiddielectric film a polymerizable monomer represented by the followinggeneral formula (8):

(wherein the substituents R⁹ and R¹⁰ each independently represent amonovalent group selected from the group consisting of a hydrogen atom,a linear or branched, saturated or unsaturated alkyl, alkoxy or alkylester group having from 1 to 10 carbon atoms, a halogen atom, a nitrogroup, a cyano group, a primary, secondary or tertiary amino group, aCF₃ group, a phenyl group and a substituted phenyl group, thehydrocarbon chains of R⁹ and R¹⁰ may combine with each other at anoptional position to form a divalent chain for forming at least one 3-,4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclicstructure together with the carbon atoms substituted by R⁹ and R¹⁰, andthe cyclic bonded chain may optionally contain a bond such as carbonyl,ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino at anyposition) with a solution containing an oxidizing agent having apolymerization initiating ability, thereby forming a composition in theform of a film of a polymer having a fibril structure on said dielectricfilm.
 11. The method for producing a solid electrolytic capacitor asclaimed in claim 7, which comprises the step of contacting on saiddielectric film a polymerizable monomer represented by the followinggeneral formula (9):

(wherein the substituents R¹¹ and R¹² each independently represent amonovalent group selected from the group consisting of a hydrogen atom,a linear or branched, saturated or unsaturated alkyl, alkoxy or alkylester group having from 1 to 10 carbon atoms, a halogen atom, a nitrogroup, a cyano group, a primary, secondary or tertiary amino group, aCF₃ group, a phenyl group and a substituted phenyl group, thehydrocarbon chains of R¹¹ and R¹² may combine with each other at anyposition to form a divalent chain for forming at least one 3-, 4-, 5-,6- or 7-membered saturated or unsaturated hydrocarbon cyclic structuretogether with the carbon atoms substituted by R¹¹ and R¹², the cyclicbonded chain may optionally contain a bond such as carbonyl, ether,ester, amide, sulfide, sulfinyl, sulfonyl and imino at any position)with a solution containing an oxidizing agent having a polymerizationinitiating ability, thereby forming a composition in the form of a filmof a polymer having a fibril structure on said dielectric film.
 12. Themethod for producing a solid electrolytic capacitor as claimed in claim7, which comprises the step of contacting on said dielectric film apolymerizable monomer represented by the following general formula (10):

(wherein the substituents R¹³, R¹⁴, R¹⁵ and R¹⁶ each independentlyrepresent a monovalent group selected from the group consisting of ahydrogen atom, a linear or branched, saturated or unsaturated alkyl,alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogenatom, a nitro group, a cyano group, a primary, secondary or tertiaryamino group, a CF₃ group, a phenyl group and a substituted phenyl group,the hydrocarbon chains of R¹³, R¹⁴, R¹⁵ or R¹⁶ may combine with eachother at any position to form a divalent chain for forming at least one3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclicstructure together with the carbon atoms substituted by R¹³, R¹⁴, R¹⁵ orR¹⁶, the cyclic bonded chain may optionally contain a bond such ascarbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino atany position) with a solution containing an oxidizing agent having apolymerization initiating ability, thereby forming a composition in theform of a film of a polymer having a fibril structure on said dielectricfilm.
 13. The method for producing a solid electrolytic capacitor asclaimed in claim 7, wherein the electrolyte having a doping action has aconcentration of from 0.001 to 2.5 mol/L.
 14. The method for producing asolid electrolytic capacitor as claimed in claim 7, wherein theconcentration of the oxidizing agent having a polymerization initiatingability is from 0.01 to 5 times the concentration of the polymerizablemonomer.
 15. The method for producing a solid electrolytic capacitor asclaimed in claim 7, wherein the step of forming a solid polymerelectrolyte is repeated from 2 to 30 times to form compositions each ofwhich is in the form of a film.
 16. A method for producing a solidelectrolytic capacitor, comprising a solid electrolytic layer composedof a polymer in layers, said polymer having an electroconductivity offrom about 0.1 to about 200 S/cm having a scaly fibrillar structure withan outer diameter in the range of about 3 nm to about 100 nm on adielectric film layer of a porous valve-acting metal, wherein thepolymer layers are formed inside a cathode and on the outer surface ofthe metal, void spaces partially remaining between adjacent polymerlayers, which comprises the step of contacting a solution havingdissolved therein a polymerizable monomer alone or together with anelectrolyte having a doping action with a single solution containing anoxidizing agent having a polymerization initiating ability kept in thesaturated or supersaturated state or a mixed solution containing theoxidizing agent and an electrolyte having a doping action on saiddielectric film, thereby forming a composition in the form of a film ofa polymer having a fibril structure on said dielectric film.
 17. Themethod for producing a solid electrolytic capacitor as claimed in claim16, wherein the polymerizable monomer has a concentration of from 0.01to 5 mol/L.
 18. The method for producing a solid electrolytic capacitoras claimed in claim 16, which comprises the step of contacting on saiddielectric film a polymerizable monomer represented by the followinggeneral formula (6):

wherein R¹ and R² each independently represent a monvalent groupselected from the group consisting of a hydrogen atom, a linear orbranched, saturated or unsaturated alkyl, alkoxy or alkyl ester grouphaving from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyanogroup, a primary, secondary or tertiary amino group, a trihalomethylgroup, a phenyl group and a substituted phenyl group, the hydrocarbonchains or R¹ and R² may combine with each other at any position to forma divalent chain for forming a 3-, 4-, 5-, 6- or 7-membered saturated orunsaturated hydrocarbon cyclic structure together with the carbon atomssubstituted by R¹ and R², the cyclic bonded chain may optionally containa bond including at least one of carbonyl, ether, ester, amide, sulfide,sulfinyl, sulfonyl and imino at any position with a solution containingan oxidizing agent having a polymerization initiating ability, therebyforming a composition in the form of a film of a polymer having a fibrilstructure on said dielectric film.
 19. The method for producing a solidelectrolytic capacitor as claimed in claim 16, which comprises the stepof contacting on said dielectric film a polymerizable monomerrepresented by the following general formula (7):

wherein the substituents R³, R⁴, R⁵, R⁶, R⁷ and R⁸ each independentlyrepresent a monovalent group selected from the group consisting of ahydrogen atom, a linear or branched, saturated or unsaturated alkyl,alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogenatom, a nitro group, a cyano group, a primary, secondary or tertiaryamino group, a CF₃ group, a phenyl group and a substituted phenyl group,the hydrocarbon chains of R³, R⁴, R⁵, R⁶, R⁷ or R⁸ may combine with eachother at any position to form a divalent chain for forming at least one3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclicstructure together with the carbon atoms substituted by R³, R⁴, R⁵, R⁶,R⁷ or R⁸, the cyclic bonded chain may optionally contain a bondincluding at least one of carbonyl, ether, ester, amide, sulfide,sulfinyl, sulfonyl and imino at any position, k represents the number ofcondensed rings surrounded by the thiophene ring and the benzene ringhaving the substituents R³ to R⁶ and is 0 or an integer of from 1 to 3,the condensed ring in the formula may contain an optional number ofnitrogen or N-oxide, with the proviso that the substituents R³ to R⁸ arededucted by the number of nitrogen or N-oxide, with a solutioncontaining an oxidizing agent having a polymerization initiatingability, thereby forming a composition in the form of a film of apolymer having a fibril structure on said dielectric film.
 20. Themethod for producing a solid electrolytic capacitor as claimed in claim16, which comprises the step of contacting on said dielectric film apolymerizable monomer represented by the following general formula (8):

wherein the substituents R⁹ and R¹⁰ each independently represent amonovalent group selected from the group consisting of a hydrogen atom,a linear or branched, saturated or unsaturated alkyl, alkoxy or alkylester group having from 1 to 10 carbon atoms, a halogen atom, a nitrogroup, a cyano group, a primary, secondary or tertiary amino group, aCF₃ group, a phenyl group and a substituted phenyl group, thehydrocarbon chains of R⁹ and R¹⁰ may combine with each other at anoptional position to form a divalent chain for forming at least one 3-,4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclicstructure together with the carbon atoms substituted by R⁹ and R¹⁰, andthe cyclic bonded chain may optionally contain a bond including at leastone of carbonyl, ether, ester, ainide, sulfide, sulfinyl, sulfonyl andimino at any position, with a solution containing an oxidizing agenthaving a polymerization initiating ability, thereby forming acomposition in the form of a film of a polymer having a fibril structureon said dielectric film.
 21. The method for producing a solidelectrolytic capacitor as claimed in claim 16, which comprises the stepof contacting on said dielectric film a polymerizable monomerrepresented by the following general formula (9):

wherein the substituents R¹′ and R¹² each independently represent amonovalent group selected from the group consisting of a hydrogen atom,a linear or branched, saturated or unsaturated alkyl, alkoxy or alkylester group having from 1 to 10 carbon atoms, a halogen atom, a nitrogroup, a cyano group, a primary, secondary or tertiary amino group, aCF₃ group, a phenyl group and a substituted phenyl group, thehydrocarbon chains of R″ and R′² may combine with each other at anyposition to form a divalent chain for forming at least one 3-, 4-, 5-,6- or 7-membered saturated or unsaturated hydrocarbon cyclic structuretogether with the carbon atoms substituted by R¹¹ and R¹², the cyclicbonded chain may optionally contain a bond including at least one ofcarbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino atany position, with a solution containing an oxidizing agent having apolymerization initiating ability, thereby forming a composition in theform of a film of a polymer having a fibril structure on said dielectricfilm.
 22. The method for producing a solid electrolytic capacitor asclaimed in claim 16, which comprises the step of contacting on saiddielectric film a polymerizable monomer represented by the followinggeneral formula (10):

wherein the substituents R¹³, R¹⁴, R¹⁵ and R¹⁶ each independentlyrepresent a monovalent group selected from the group consisting of ahydrogen atom, a linear or branched, saturated or unsaturated alkyl,alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogenatom, a nitro group, a cyano group, a primary, secondary or tertiaryamino group, a CF₃ group, a phenyl group and a substituted phenyl group,the hydrocarbon chains of R′³, R, R or R′⁶ may combine with each otherat any position to form a divalent chain for forming at least one 3-,4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclicstructure together with the carbon atoms substituted by R¹³, R¹⁴, R¹⁵ orR¹⁶, the cyclic bonded chain may optionally contain a bond including atleast one of carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyland imino at any position, with a solution containing an oxidizing agenthaving a polymerization initiating ability, thereby forming acomposition in the form of a film of a polymer having a fibril structureon said dielectric film.
 23. The method for producing a solidelectrolytic capacitor as claimed in claim 16, wherein the polymerizablemonomer has a concentration of from 0.01 to 5 mol/L.
 24. The method forproducing a solid electrolytic capacitor as claimed in claim 16, whereinthe electrolyte having a doping action has a concentration of from 0.001to 2.5 mol/L.
 25. The method for producing a solid electrolyticcapacitor as claimed in claim 16, wherein the concentration of theoxidizing agent having a polymerization initiating ability is from 0.01to 5 times the concentration of the polymerizable monomer.
 26. Themethod for producing a solid electrolytic capacitor as claimed in claim16, wherein the step of forming a solid polymer electrolyte is repeatedfrom 2 to 30 times to form compositions each of which is in the form ofa film.
 27. A method for producing a solid electrolytic capacitorcomprising a solid electrolytic layer composed of a polymer having afibril structure on a dielectric film layer of a porous valve-actingmetal, which comprises the step of contacting a polymerizable monomerwith a single solution containing an oxidizing agent having apolymerization initiating ability kept in the saturated orsupersaturated state or a mixed solution containing the oxidizing agentand an electrolyte having a doping action on said dielectric film,thereby forming a composition in the form of a film of a polymer havinga fibril structure on said dielectric film, wherein the oxidizing agenthaving a polymerization iitiating ability is at least one compoundselected from persulfates, bichromates and trivalent iron salts.
 28. Amethod for producing a solid electrolytic capacitor comprising a solidelectrolytic layer composed of a polymer having a fibril structure on adielectric film layer of a porous valve-acting metal, which comprisesthe step of contacting a solution having dissolved therein apolymerizable monomer alone or together with an electrolyte having adoping action with a single solution containing an oxidizing agenthaving a polymerization initiating ability kept in the saturated orsupersaturated state or a mixed solution containing the oxidizing agentand an electrolyte having a doping action on said dielectric film,thereby forming a composition in the form of a film of a polymer havinga fibril structure on said dielectric film, wherein said oxidizing agenthaving a polymerization initiating ability is at least one compoundselected the group consisting of from persulfates, bichromates andtrivalent iron salts.